CANADIAN MEDICAL PHYSICS NEWSLETTER nterACTIONS Le BULLETIN CANADIEN de PHYSIQUE MÉDICALE

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PUBLICATIONS MAIL AGREEMENT NO. 40049361 RETURN UNDELIVERABLE CANADIAN ADDRESSES TO: BARB CALLAGHAN C/O NOLAN DRUGS POST OFFICE 8901 118th AVENUE EDMONTON, AB T5B 0T5

A publication of the Canadian Organization of Medical Physicists and the Canadian College of Physicists in Medicine http://www.medphys.ca Images from prototype MVCT ISSN 1488-6847 scanner in Cobalt-60 beam

51 (2) avril/April 2005 About our Cover COMP EXECUTIVE These images were obtained by a prototype, bench-top, third generation megavoltage computed tomography (MVCT) scanner in a Co60 beam. The Chair: system uses an 80-element detector array of CdWO4 crystals and photodiodes, Mr. Peter O’Brien arranged on an arc of radius 110 cm. This phantom (module CTP612 in Toronto-Sunnybrook Regional CATPHAN500, Phantom Labs) was especially designed for MVCT, and Cancer Centre 2075 Bayview Avenue consists of inserts at 3%, 2.5% and 1.5% nominal contrast levels. Each contrast Toronto, ON, M4N 3M5 level has cylinders of diameters 2, 0.4, 0.5, 0.6, 0.7, 0.8 and 1.5 cm, and there is Tel: (416) 480-4622 a central cylinder of 0.4 cm diameter with a contrast level of 1.5 %. The dose to Fax: (416) 480-6801 the centre of the phantom was estimated to be approximately 17 cGy when all peter.o’[email protected] the projections were used in the reconstruction process. Images with doses of Past Chair: 8.5, 4.3 and 2.1 cGy were obtained by utilising only one-half, one-fourth and Dr. Clément Arsenault one-eighth of data pulses per revolution, respectively. The figure shows images Dr. Leon Richard Oncology Centre of CTP612 module at four different dose levels, (a) 17 cGy, (b) 8.5 cGy, (c) 4.3 Hôpital Dr. Georges-L. Dumont 37 rue Providence cGy and (d) 2.1 cGy. Groups A, B and C have measured contrast levels of 2.1%, Moncton, NB, E1C 8X3 1.9% and 2.8% respectively while the cylinder in the middle has a contrast of Tel: (506) 862-4151 1.5% in Co60 with respect to the background material in the phantom. All the Fax: (506) 862-4222 images have been windowed and levelled in the same way. The bench-top [email protected] MVCT provides a contrast resolution of 1.5% at 0.6 cm diameter using a dose of Chair Elect: 2.1 cGy. Dr. Stephen Pistorius CancerCare Manitoba Images provided by T. Monajemi1, D. Tu1, D. Rickey2, S. Rathee1, and G. 675 McDermot Avenue 1 Winnipeg, MB, R3E 0V9 Fallone ; 1. Cross Cancer Institute and University of Alberta, Edmonton, AB., 2. Tel: (204) 787-4134 CancerCare Manitoba and University of Manitoba, Winnipeg, MB Fax: (204) 775-1684 [email protected]

Secretary: The Canadian Medical Physics Newsletter, which is Job advertisements should be submitted to: Dr. William Ansbacher a publication of the Canadian Organization of Dr. Julian Badragan BC Cancer Agency Medical Physicists (COMP) and the Canadian Col- Tom Baker Cancer Centre 2410 Lee Street lege of Physicists in Medicine (CCPM) is published 1331-29 Street NW Victoria, BC, V8R 6V5 four times per year on 1 Jan., 1 April, 1 July, and 1 Calgary, AB, T2N 4N2 Tel: (250) 519-5621 Oct. The deadline for submissions is one month E-mail: [email protected] FAX: (250) 519-2024 before the publication date. Enquiries, story ideas, Phone: (403) 944-4598 [email protected] images, and article submissions can be made to: Fax: (403) 944-2397 Treasurer: Dr. Boyd McCurdy Mr. Horacio Patrocinio CancerCare Manitoba Job Advertising Options McGill University Health Centre 675 McDermot Avenue 1650 avenue Cedar Winnipeg, Manitoba, R3E 0V9 OPTION 1 ($200): Job posting on COMP/CCPM Montréal, PQ, H3G 1A4 Email: [email protected] website only (updated monthly) Tel: (514) 934-8052 Phone: (204) 787-1966 OPTION 2 ($300): Job posting on COMP/CCPM Fax: (514) 934-8229 Fax: (204) 775-1684 website AND in InterACTIONS! (single page) [email protected] Members of the Editorial Board include: OPTION 3 ($300): Job posting is immediately e- Councillor for Communica- Peter Munro: [email protected] mailed to COMP/CCPM members (no website or InterACTIONS! posting) tions: Pat Cadman: [email protected] Mr. Darcy Mason Darcy Mason: [email protected] Cancer Centre for the Southern Interior 399 Royal Avenue Please submit stories in Publisher 98, Word 6.0, Kelowna, BC, V1Y 5L3 Word 97, or ASCII text format. Hardcopy submis- Tel: (250) 712-3917 sions will be scanned to generate an electronic Fax: (250) 712-3911 document for inclusion in the Newsletter. Images [email protected] in Tiff format at 300 dpi resolution are preferred. Regular Advertising Councillor for Professional All contents of the Newsletter are copyright of Affairs: Canadian Organization of Medical Physicists and 1/2 page 1 Addn. the Canadian College of Physicists in Medicine. page pages Dr. Peter McGhee Please do not reproduce without permission. Thunder Bay Regional Health Sciences Member $100 $100 Centre Announcement 980 Oliver Road Corporate advertising enquiries can be made (until Corporate Thunder Bay, ON, P7B 6V4 a new Executive Director is found) to: Member $150 $200 $100 Tel: (807) 684-7325 Dr. Boyd McCurdy Non Profit Fax: (807) 684-5801 CancerCare Manitoba Organisation $225 $300 $125 [email protected] 675 McDermot Avenue Corporate Non- Winnipeg, Manitoba, R3E 0V9 Member $300 $400 $200 Email: [email protected] Phone: (204) 787-1966 Color Add $400 (when available) Fax: (204) 775-1684 InterACTIONS 51 (2) avril/April 2005 CCPM BOARD

Inside this issue: President: Dr. Brenda Clark Medical Physics Division BC Cancer Agency Optimization in Intensity Modulated 600 West 10th Ave. Radiotherapy ...57 Vancouver, BC, V5Z 4E6 Tel: (604) 877-6000 Stewart Gaede and Eugene Wong FAX: (604) 877-6059 [email protected] Vice-President: Dr. Dick Drost Nuclear Medicine Department St. Joeseph’s Health Care London 268 Grosvenor Street London, ON. N6A 4V2 Tel: (519) 646-6100 x64141 FAX: (519) 646-6135 [email protected] Registrar: Message From the COMP Chair – Peter O’Brien 44 Dr. Wayne Beckham Vancouver Island Cancer Centre Message From the CCPM President – Brenda Clark 45 2410 Lee Street Victoria, BC, V8R 6V5 Message From the Executive Director of COMP/CCPM – Nancy Barrett 46 Tel. (250) 370-8225 Report on Great Lakes AAPM Chapter Meeting — Jake Van Dyk 47 FAX: (250) 370-8697 [email protected] 30 years ago: First PET scanner in Canada — Chris Thompson 48

ACROSS CANADA — Toronto-Sunnybrook, St. John’s 50 Chief Examiner: Dr. Katharina Sixel Proposed CCPM By-Law Amendments — Brenda Clark 52 Toronto-Sunnybrook Regional Cancer Centre Report on WesCan 2005 — Matt Schmid 54 2075 Bayview Avenue WesCan 2005 Conference Abstracts 55, 56, Toronto, ON, M4N 3M5 67-74 Tel: (416) 480-5000 ext. 1095 FAX: (416) 480-6801 [email protected] Secretary-Treasurer: Corporate Members 75 Dr. Narinder Sidhu Advertising 60, 61, Saskatoon Cancer Centre 74, 76-80 20 Campus Drive Saskatoon, SK S7N 4H4 Tel: (306) 655-2696 Fax: (306) 655-2701 [email protected] General Board Members: Dr. John Andrew Mr. Michael Evans Dr. John Rowlands

COMP/CCPM Office Ms. Barb Callaghan COMP Secretariat COMP/CCPM Office PO Box 39059 Edmonton, AB, T5B 4T8 Telephone: (780) 488-4334 Facsimile: (780) 482-4425 [email protected] Message from the COMP Chair:

As promised in the last Interactions, (www.cap.ca). There are also commemorative we have now completed the process for hiring items (mugs, t-shirts etc) available through a new executive director for COMP and the the CAP. CCPM. We were fortunate to have several good candidates for this position. Brenda Hopefully when this article is printed winter Clark and I interviewed the finalists and after weather will be behind us. With renewed consulting with the COMP executive and the energy we can begin the last stages of CCPM board we have agreed to a 2-year planning for the annual COMP meeting in contract with Ms. Nancy Barrett and her Hamilton, July 7-9. I must thank Darcy firm, Association Management, Consulting Mason for the time and effort that he has put and Evaluation Services. Nancy was into the preparation for the meeting. We have introduced as the new executive director in an used a new AAPM sponsored abstract service email sent in January to all COMP members. This contract will bring stability and continuity to this very important COMP position. Nancy will be the face of COMP, acting as the main point of contact for our We expect that commercial colleagues, for other medical physics associations and for other groups. Nancy will be at the annual meeting and is this new leader- anxious to meet as many COMP and CCPM members as possible. We expect that this new leadership will add significantly to the ship [Nancy profile of our organization and will add value for the members. However, there will be a cost. At the AGM this summer a proposal Barrett] will add will be put forward to increase membership fees, partially in response to our new leadership model. significantly to Plans for the COMP Gold Medal are progressing although the input from the the profile of our members for the medal design has been unimpressive. At this writing I am not aware of 1 submission!. However, I am very pleased Mr. Peter O’Brien, COMP Chair organization and to announce that Dave Rogers has agreed to this year (AMOS) and Darcy as chair of the be the chair of the selection committee. Dave communications committee has led the effort will prepare the terms of reference for the to adapt this to our needs. Joe Hayward and will add value award and will present these to the executive his local arrangements team have done an at the annual meeting in July. outstanding job preparing for the COMP meeting and I hope that you will support them for the members. 2005 is the World Year of Physics (WYP). with your attendance. I look forward to seeing While the World Year of Physics was so- everyone in Hamilton. named by the International Union of Pure and Applied Physics (IUPAP), the UN General Assembly passed a resolution in June 2004 that 2005 be the “International Year of Physics”. There may be some confusion but both names refer to the same thing and WYP is the term adopted in Canada. All physics associations in Canada have been asked by the Canadian Association of Physicists to plan events to commemorate this year. The first COMP public lecture is the main event planned by COMP for the WYP. You can check out the range of events available (including the COMP public lecture and the COMP conference) on the CAP website

44 51(2) avril/April 2005 Canadian Medical Physics Newsletter / Le bulletin canadien physique médical Message from the CCPM President:

I will start by welcoming Nancy Bar- tion, to be held on Saturday, 19 March. This rett to her new position as Executive Direc- year, 18 candidates will write this examination tor of our two organisations. I am looking in centres across the country. The success of forward to working with Nancy and her this examination each year is a result of consid- team at AMCES. erable effort on the part of many Medical Physicists across Canada, most of whom re- In my last editorial, I mistakenly stated that main nameless in the interests of anonymity. Margaret E. J. Young was our first Chief Clearly all the invigilators give up a Saturday Examiner. She wrote to me recently to point for this task. Also, the work of setting ques- out that Harold E. Johns was the initial tions and marking papers is time consuming Chairman of the Examining Board and Mar- and cannot be described by any criterium as ex- garet was chairman of the examiners for the citing! We very much appreciate the dedication ...we are propos- oral exams. Margaret writes: to our certification program shown by all these “Just for the record, there were volunteers. slightly different examiners for the ing... to divide written and oral parts for each spe- Elsewhere in this edition of InterACTIONS you will find the notice of this year’s proposed changes to the CCPM Bylaws for voting at the up the long AGM in Hamilton. The most important change we are proposing is to modify sections III and IV of the written Membership examination by questions where re-publishing the question bank in the form of a larger number of shorter questions. Many of the comments/suggestions we have had over the appropriate into years has been to the effect that the examination as it is currently structured with the selection of only two out of a possible 30 long questions in- several smaller trinsically restricts the scope of the questions that are asked. The solution that we are propos- ing is to divide up the long questions where ap- ones such that propriate into several smaller ones such that several questions could be selected each year for the examination. In this way, a wider range several ques- of topics could be tested. This strategy would also make it easier to revise and update the questions, a task that is required each year to tions could be ensure the examination remains relevant. Dr. Brenda Clark, CCPM President Clearly some effort would be required to ensure that an appropriate depth of knowledge was selected each cialty. For the radiation oncology also addressed and that the shorter questions section, the examiners who set and did not translate into a less rigorous examina- marked the written papers were tion. year for the Harold Johns, Doug Cormack, Jack Cunningham, and myself with Please write to us if you have any comments or Harold being the chairman, while suggestions on our proposals or other activities. [MCCPM] for the oral, the examiners were We are always seeking input, whether you are a Jack Cunningham, John Mac- current or a potential member. Donald, Roger Mathieu and myself examination. . as chairman.” Thank you, Margaret, for this clarification and for sending a complete list of all the original examiners for all specialties for our archives.

As I write this message in early March, our Chief Examiner, Katharina Sixel, and her team of invigilators and examiners are pre- paring for the written Membership examina-

Canadian Medical Physics Newsletter / Le bulletin canadien physique médicale 51(2) avril/April 2005 45 Message from the Executive Director of COMP/CCPM:

I am pleased to make my first and the Local Arrangements Committee are submission to InterACTIONS since taking on working hard on this important event! the role of Executive Director of COMP/ CCPM. Thank you for your wonderful In the meantime, please feel free to contact welcome and support during this time of me in Ottawa with your ideas and suggestions transition. or to just say hello. I can be reached at 613- 599-1948 or at [email protected]. As I write this article, the 2005 federal budget has just been released and the Canadian Consortium for Research, of which COMP is a member, has expressed a mixed reaction. While a modest increase (less than 3%) in research-granting council budgets was announced and the Canadian Academies of Science and Genome Canada received funding, there were no new initiatives to I look forward to address the challenges faced by post- secondary institutions. working with As you are aware, health care and education are the top two concerns of Canadians and COMP/CCPM must work, in conjunction members, volun- with other organizations, to promote the benefits of increased capacity in research, post-secondary education and scientific teers and part- knowledge in Canada to address these concerns. ners to profile The United Nations has declared 2005 as the International Year of Physics. This is a tremendous opportunity to acknowledge the the contribution progress and importance of this great field of science and COMP/CCPM are doing just that by conducting their first public lecture in and competency conjunction with the 2005 annual conference Ms. Nancy Barrett, in Hamilton. This is an exciting initiative and COMP/CCPM Executive Director an opportunity for the general public to learn of medical more about medical imaging and actually get a “view from inside”. Dr. Michael Bronskill of the University of Toronto will deliver this physicists in lecture.

I have been involved with the association/not- Canada... for-profit sector for the past eight years and am pleased to have an opportunity to serve COMP/CCPM. I look forward to working with members, volunteers and partners to profile the contribution and competency of medical physicists in Canada, to identify and address issues facing the profession and to facilitate the exchange of information and research.

Thank you to the many volunteers and to Barb Callaghan for making my first three weeks a most positive experience. I look forward to meeting you in Hamilton at the 2005 conference. I know that Joe Hayward

46 51(2) avril/April 2005 Canadian Medical Physics Newsletter / Le bulletin canadien physique médical Report on Great Lakes AAPM Chapter Meeting Submitted by Jake Van Dyk London Regional Cancer Program , London, ON

One of the largest and most successful meetings of the Great Lakes Chapter (GLC) of the American Association of Physicists in Medicine (AAPM) was held in London, Ontario on Saturday 6 November 2004. On 17 June 2004, Jean Moran, President of the GLC AAPM e-mailed Jake Van Dyk to see whether London would be interested in hosting the fall Young Investigators’ Symposium (YIS) of the GLC. She thought that the Chapter members might be interested in seeing the London tomotherapy unit. Jake responded with two questions: (1) When is the usual date? and (2) How many people usually attend? Jean’s response: 23 October or 6 November 2004 and usually 5 or 6 people participate in the YIS with a total of 20-30 people participating in the meeting. Jean also suggested inviting Rock Mackie from Madison WI to speak on helical tomotherapy. Jake suggested adding David Jaffray to the program to generate a discussion on the competing modalities of cone beam CT and helical tomotherapy. The net result was a meeting that involved 16 young investigators and a symposium on Image-Guided Therapy which included Rock Mackie, David Jaffray (Princess Margaret Hospital, Toronto), Tomas Kron (London Regional Cancer Program, London, Ontario), Fang-Fang Yin (Duke University, formerly from Henry Ford Hospital in Detroit). The meeting had >140 attendees as well as 11 commercial exhibitors. People traveled from as far as Hawaii to attend. The Tomas Kron – Tomotherapy tour guide at the GLC-AAPM day was rounded out with a panel discussion moderated by meeting. Picture courtesy of Randy Ten Haken. Colin Orton on Cone Beam CT versus Tomotherapy. The winner of the YIS was Dylan C Hunt (co-authored by John Rowlands) of Sunnybrook Health Sciences Centre/University of Toronto. The event was a tremendous success and is being talked about as one of the largest AAPM chapter meetings ever.

Students who presented at the GLC-AAPM YIS Pictured are (Back Row, from left to right): Rojano Kashani, Neelam Tyagi, Sean A Graham, Steven Babic, Bryan Kim, Bryan Schaly, Mike Oliver, and Andreas W Rau. (Front Row, from left to right): Mihaela Rosu, Jeff Small, Martha M Coselmon, Andrea McNiven, Alexandra Rink, Dylan C Hunt, and William Song. (Missing from picture is Zhouping Wei). Picture courtesy of Randy Ten Haken.

Canadian Medical Physics Newsletter / Le bulletin canadien physique médicale 51(2) avril/April 2005 47 30 Years Ago: First PET Scanner in Canada Submitted by Chris Thompson invasively. One of these techniques involved applying small Montreal Neurological Institute, silicon diode radiation detectors and administrating Xe-133 and Montreal, QC measuring the “washout” of this inert gas in the exposed brain. The other involved injecting fluoresceine dye into the blood and In April 1975 Ernst Meyer, (the late) Lucas Yamamoto, taking rapid sequences of photographs to study the passage of and I drove to the Brookhaven National Laboratory on Long the dye through the blood vessels and the exposed cortex. The Island and returned with the first instrument for positron positron emitting isotope Kr-77, could perform the same emission tomography (PET) in Canada. Thirty years ago, “PET” function as the Xe-133 and the generator produced Ga-68 was a domestic animal, not a medical imaging technique. To EDTA could measure the blood transit time and breakdown of many or you reading this today, PET, and better still PET/CT, is the blood-brain barrier. Since all of the studies involved using a something that your department “has” or “wants” to improve the computer, and I had been involved in getting them to work, I work-up and radio-therapy treatment planning of cancer was expected to get the “head shrinker” to work as well! patients. This is a relatively recent phenomenon, and even though PET has been around for over 30 years, it had very little There had been a few trips to Brookhaven to look at the impact on the lives of most Medical Physicists until 10 years instrument, and to negotiate the “loan” of it to the MNI. During ago with the advent of whole-body PET scanning with the these trips, I became familiar with the detectors, amplifiers and glucose analog commonly known as FDG. circuits which detected coincident gamma rays from positron annihilation, as well as the program which was supposed to Soon after the Montreal Neurological Institute (MNI) reconstruct the images. I was quite familiar with the way the acquired the first CT scanner in 1973, interest in other “EMI-scanner” reconstructed images, but had no idea how the tomographic imaging modalities was initiated. Lucas algorithm used by the Brookhaven group worked [1]. I did Yamamoto had worked at the Brookhaven National Lab. (BNL) know that it took a long time on the Lab’s main-frame computer of the US Department of Energy for several years before and I was expected to get it working on a PDP-12 with 16K of coming to the MNI. He often talked about a device, that he had memory. (That’s right 16,384 12-bit words!). One day we were worked on while at BNL known as the “head shrinker”, that was in the small on-site hospital negotiating the transfer. During a now unused. He was convinced that if it was in Montreal it break, I looked at a display of occupational therapy where would work, even though it had never performed satisfactorily patients had made patterns by stringing coloured yarn over in Brookhaven. He, and the director of the MNI, Dr William arrays of nails. Many patterns were possible and some were Feindel, had perfected two techniques for investigating regional very pretty. It occurred to me that these nails were like the ring cerebral blood flow (rCBF)in the exposed brain, both in animal detectors in the scanner, and the yarn between two nails experiments and during human surgery for arterial-venous represented the lines of response of the each pair of detectors. If malformations and certain highly vascular brain tumours. They they were organized in the correct way, they would look like the saw this instrument as being able to measure rCBF non projections in a CT scanner. Instead of the attenuation along each line we would have the number of counts acquired during the time of a study. So perhaps the same algorithm used in CT scanners would work here.

At Brookhaven, the original concept had the patient sitting in a chair and the detectors were arranged in a hemisphere and looked rather like a strange hair dryer. By the time I was involved with it, the detectors were arranged in a single ring. There were 32 1" diameter NaI crystals and PMTs, the even ones inserted radially and the odd ones axially. We decided that the patients would be scanned supine like in a CT scanner, and had a stand built for them. I did not think that patients would like being told that the device was called the “head shrinker” and decided that “Positome” would be a better name. Figure 1: Original Positome configuration. (Continued on page 49)

48 51(2) avril/April 2005 Canadian Medical Physics Newsletter / Le bulletin canadien physique médical 30 Years of PET in Canada…. (Continued from page 48) One of the images included here is what Dr. Feindel believes to be the first image of a glioblastoma made with PET. The Positome was installed on the second floor of the This was made with Ga-68 EDTA after an initial dynamic MNI, as shown in Figure 1, and a cable was run up to the 7th study. The 68 minute half-life allowed “static” images through floor where the computer was. The programs for acquisition of several slices through the brain. the scans, reconstruction, and display were initiated on a Tektronix graphics terminal. This had a storage screen (like a The first paper we wrote about PET [3] was presented in big storage oscilloscope screen) with both a character generator, August 1975 at a conference in Stanford Ca. At that time we and 1024 by 768 addressable points. The images were had still not performed any patient studies. A more complete reconstructed using the Shepp and Logan algorithm, see figure report on its performance and use in clinical studies appeared 2, which was published in 1974 [2]. This simple technique was the following year[4]. able to reconstruct 32 x 32 images in less than 30 seconds on a computer with a clock speed of 0.5 MHz. The Brookhaven In 1978 we made Positome II which was the first PET algorithm (which involved inversion of the Radon transform) scanner to use bismuth germanate detectors. This new, high was run as a batch job on a main-frame computer and the density, scintillator became the mainstay in PET for over 25 images were not available until the next day. years.

This Positome was used for three years. One or two days 1) Shepp L A, and Logan B F: The Fourier Reconstruction of a a week we could get Kr-77 from the cyclotron in the Foster Head Section. IEEE Trans. Nucl. Sci. NS-11:21-38 (1974) laboratory of the McGill Physics Department. The gas was trapped in a U-tube immersed in liquid nitrogen, then sealed. 2) Marr RB, On the Reconstruction of a Function on a Circular Ernst Meyer, who did all the data analysis for our studies then Domain from a Sampling of its Line Integrals. J. Math. carried this tube in a lead pot about one block up University St Anal. and App. 357-374 (1974) from the Foster lab. to the MNI. (The half- life of Kr-77 is just over an hour, so he did not have to run!) On other days we used 3) Thompson C J, Yamamoto Y L and Meyer E: "Positron Ga-68 EDTA from a Ge-68/Ga-68 generator. The software emission tomography: reconstruction of images from a allowed dynamic studies which were displayed on the terminal multiple coincidence detector ring". Proc. Amer. Optical Soc screen by intensifying a pseudo-random array of 7x7 sub-pixels Meeting on Image Processing for 2D and 3D Reconstruction which formed each of the 32x32 image pixels to simulate from Projections. pp. TuA4-1 to TuA4-4, (Aug. 1975) shades of grey in a similar fashion to a dot matrix printer. They were painted on the storage screen where they were stable for a 4) Thompson C J, Yamamoto Y L and Meyer E: "A positron few minutes or until erased. The display software allowed for imaging system for the measurement of regional cerebral multiple images to be displayed, regions of interest to be blood flow." Proc. Soc. Photo Optic Instrument Engineers: selected, and the display log-linear time-activity plots from 96: Optical Instrumentation in Medicine V, 263-268 which the washout or transit time was estimated from the down- (1976) slope of a fitted line.

Figure 2: Shepp-Logan reconstruction code.

Figure 3: Glioblastoma Ga-68 EDTA from 1975.

Canadian Medical Physics Newsletter / Le bulletin canadien physique médicale 51(2) avril/April 2005 49 Across Canada

It is not possible to describe each person’s role in this short article but each physicist does have several well-defined clinical responsibilities and all new developments or major programs are handled in an interdisciplinary team based way. The largest sub-unit in the physics group is the treatment planning group, Toronto Sunnybrook Regional Cancer led by our Senior Planning Physicist Kathy Mah. Centre, and University of Toronto, We are now commissioning a new Pinnacle TPS with plans for Toronto, ON implementation to be completed over the summer. This is part Submitted by Peter O’Brien of a major effort to integrate much of our planning activity, now spread out over about 10 different commercial systems. We are The Toronto Sunnybrook Regional Cancer Centre (TSRCC) is a also in the middle of a conversion to the IMPAC radiotherapy program of the Sunnybrook and Women’s College Health data management system. We are now filmless and hope to be Science Centre (S&W), located in north Toronto. The TSRCC is paperless at the end of this process. organized along program lines - the Medical Physics Department is completely within the Radiation Program and Academically, most physicists are appointed to the department includes physicists, physics technologists, mechanical and of Radiation Oncology (University of Toronto). The DRO electronics technologists, secretaries and students. We now includes radiation oncologists, medical physicists and some have 15 physicists in a total full-time staff of 45. The radiation therapists from both the Sunnybrook Regional Cancer department supports radiation treatment planning and delivery Centre and the Princess Margaret Hospital. Several physicists for approximately 5700 new patients each year. Our equipment also have appointments with the department of Medical includes 12 linear accelerators, 1 cobalt unit, orthovoltage, 2 Biophysics (U of T) and graduate students are typically CT-simulators, 1 conventional simulator and 1 PET/CT registered in that department. simulator. Research activity is in several areas: We support a wide range of clinical programs from stereotactic x Target definition (Mah, Sixel, Basran), including radiosurgery to intravascular brachytherapy. Many of the defining the role of PET/CT planning in radiation treatment techniques that we use were developed locally. A new therapy planning and development of functional CT. development at the TSRCC (described in Interactions – January x Imaging for Radiation Therapy (Pang, Rowlands, 2005) is partial breast irradiation using implanted Palladium Yeboah, O’Brien), including the development of seeds. (Continued on page 51)

A picture of the physics crew is above: the physicists are scattered throughout-starting in the bottom row: Kathy Mah, Beibei Zhang (resident); second row: Raxa Sankreacha; third row: Collins Yeboah, David Beachey, Geordi Pang, John Rowlands (Head of Medi- cal Physics Research), Alec Lightstone, Stan Szpala (resident); back row: Nelson Videla, Milton Woo, Daryl Scora, Peter O’Brien, Brian Keller, Bryan Schaly (resident) and Parminder Basran. Missing are Katharina Sixel, William Que and Stuart Burnett (resident). Many of you will have talked to the person in the red jacket, in the middle of the photograph, our secretary Rose Lisi.

50 51(2) avril/April 2005 Canadian Medical Physics Newsletter / Le bulletin canadien physique médical ACROSS CANADA… (Continued from page 50) two electronic technologists. systems for MVCT xDetector Technology (Rowlands, Pang) Our equipment includes two Varian dual energy linacs with 120 xBrachytherapy (Keller, Sankreacha, Que, Pignol (Rad. leaf MLC, aSi Portal Imaging, a Co-60 unit, a 250kV x-ray unit, Onc)), including a novel partial breast irradiation a Nucletron LDR remote afterloading system, a Philips large- technique using Palladium-103 seeds. bore AcqSim CT scanner, a Ximatron conventional simulator, xIntermediate Photon Energy Tomotherapy (iPET) Eclipse Treatment Planning System and Varis/Vision Record (Pignol, Beachy, Keller) and Verify System. We have purchased a GammaMed HDR afterloader and the BrachyVision treatment planning system Research is supported by grants from NCIC, U.S Army, CBRF, with installation planned for Spring 2005. CHIR, NSERC and industry. As a small centre that had been understaffed for many years in Many physicists teach courses at the U of T, at Ryerson the past, our current projects are all clinical in nature. These University and at the Michener Institute. There is also an include the development of an HDR program, commissioning initiative underway to completely restructure the medical enhanced dynamic wedge and implementing the RadCalc physics residency program as a joint TSRCC/PMH professional Monitior Unit check program. We recently implemented a diploma through the Department of Radiation Oncology at the prostate protocol using implanted gold seeds for localization University of Toronto. and a 6-field conformal treatment technique. We have completed an extensive review of our QA program for linacs After 2 decades of constant growth in patient numbers, the and updated our program to include more MLC and Portal Toronto Sunnybrook Regional Cancer Centre has now reached a Imaging tests to meet the COMP and AAPM standards. We are relatively stable position in that regard. We are now ready to now reviewing the CT Sim QA and treatment planning system embark on a different stage of our growth – with much more QA in the same manner. emphasis on grant-supported independent researchers, to create a balanced academic and clinical department. As our treatment hours are 8am-6pm and we have a waiting list for treatment, we are proposing an expansion to our facility to include two new treatment rooms – it is amazing how quickly you run out of space!

We are looking forward to the expansion of our projects as our staff remains stable and is gaining experience. We were happy to host the 2004 Atlantic Medical Physics Group Meeting last fall.

In April 2005, the NCTRF will be amalgamated into a larger health board: the Newfoundland and Labrador Eastern Newfoundland Cancer Treatment and Regional Integrated Health Authority. It remains to be seen Research Foundation; what impact this will have on the Provincial Cancer Program. Dr. H. Bliss Murphy Cancer Centre, St. John’s, NL Submitted by Maria Corsten

The Newfoundland Cancer Treatment and Research Foundation (NCTRF) was established in 1971 as a provincial health care organization. It is a province-wide organization with a mandate to meet the needs of Newfoundlanders and Labradorians in cancer prevention, treatment and support and research. The NCTRF operates the Dr. H. Bliss Murphy Cancer Centre in St. John’s and regional oncology programs throughout the province. In 1999, our organization was awarded Accreditation with the Canadian Council on Health Services Accreditation.

The Dr. H. Bliss Murphy Cancer Centre provides the only Radiation Oncology Department and Services for the entire province on Newfoundland and Labrador. We treat ~1200 Radiation Therapy patients per year.

The Department of Medical Physics and Electronics has grown significantly in the past few years. The department, headed by NCTRF Medical Physicsts, from left to right: NY Feng, Maria Corsten has five physicists (NY Feng, Donia MacDonald, Michael Gillard, Maria Corsten, David Goodyear and Do- Michael Gillard and David Goodyear), three dosimetrists and nia MacDonald

Canadian Medical Physics Newsletter / Le bulletin canadien physique médicale 51(2) avril/April 2005 51 Proposed Bylaw Amendments - 2005

The Board of the CCPM hereby gives notice that we will be seeking ratification of the following Bylaw amendments at the Annual General Meeting in July 2005 in Hamilton, Ontario. The proposed changes are in bold, italic and underlined.

1 THE ADDITION OF A DEPUTY CHIEF EXAMINER

RATIONALE: The duties of the Chief Examiner have recently been substantially increased with the addition of an oral examination at the Membership level. The aim of adding a Deputy Chief Examiner is to distribute some distribution of the work involved in the whole examination process and also to ensure a smooth transition be- tween Chief Examiners.

ARTICLE IV: OFFICERS AND GOVERNING BODIES

Add a sixth executive officer “6) Deputy Chief Examiner”

Also, after the section describing the “Duties of the Chief Examiner”,

Add “Duties of the Deputy Chief Examiner The Deputy Chief Examiner shall assist the Chief Examiner in the exami- nation processes.”

2 MODIFICATION OF THE WRITTEN MEMBERSHIP EXAMINATION STRUCTURE

RATIONALE: The current structure requires that two questions from the 30 question bank be randomly selected for Sections III and IV of the examination. We are proposing that the question banks be revised to give more than 30 shorter questions to enable a wider selection of topics to be addressed in each examination through the selection of a number of shorter questions. This change in the wording of the Bylaw Appendix would provide that flexibility.

APPENDIX III: EXAMINATIONS, Membership Written Examination

Section II and IV Change “This portion of the examination is based on a question bank specific to the applicant's sub- specialty available to the applicant at least three months prior to the exam by the first of October prior to the examination. Each sub-specialty bank contains thirty questions.” Add The question bank will be posted on the CCPM web site together with more specific information regarding the upcoming examination. The questions for Sections III and IV will be chosen at random from the bank. (Continued on page 53)

52 51(2) avril/April 2005 Canadian Medical Physics Newsletter / Le bulletin canadien physique médical (Continued from page 52)

Delete “Section III contains one question chosen at random from the twenty questions in the bank specific to the sub-specialty.”

Delete “Section IV contains one question chosen at random from the remaining ten questions which cover more general areas of the sub-specialty.”

3 AMENDMENT OF BYLAWS

RATIONALE: Currently the Bylaws request proposals for additions, corrections or amendments of the Bylaws to be forwarded to the Registrar. With the addition of a Secretary/Treasurer in 1994, it is now more appropriate for this person to be responsible for these proposals.

ARTICLE VIII Replace (2) Proposals for additions, corrections or amendments to the bylaws should be forwarded to the Registrar Secretary/Treasurer by means of … Replace (3) The Registrar Secretary/Treasurer shall submit any such proposals ...

4 DELETION OF INFORMATION ABOUT WHO DOES NOT REQUIRE CERTIFICATION

RATIONALE: It was decided at the mid-year board meeting that it was not the business of the college to give advice as to who does not require certification.

APPENDIX I: CERTIFICATION

Delete Who does not need to be "certified" 1. Medical Physicists who work in industry and do not provide any medical physics con- sultation services to medical institutions. 2. Medical Physicists who work at universities and are involved in teaching and research, and whose work is not related to patient care. 3. Medical Physicists who work for regulatory agencies and whose work is not related to patient care.

Canadian Medical Physics Newsletter / Le bulletin canadien physique médicale 51(2) avril/April 2005 53 Report on WesCan 2005

Submitted by Matt Schmid cancer followed by a more effective system of treating the can- Allan Blair Cancer Centre, Regina, SK cers that can’t be prevented would greatly reduce the impact of cancer on the population. He openly stated that reducing the im- The 2005 version of the Western Canada Medical Physics Meet- pact of cancer on the population would be one of the legacies of ing (WESCAN) was held March 16 -19 in Calgary. WESCAN the substantial revenues generated by the oil industry in Alberta. has always been a relatively informal venue for physicists, therapists, dosimetrists, mould room and electronics staff, stu- Among other topics, Dr. Larsson addressed the challenges re- dents, and other cancer care specialists to meet with their col- lated to the escalating costs of cancer treatment. The increase in leagues in western Canada to strengthen both professional and costs is largely (but not entirely) due to the stunning increase in social ties. This year, the conference drew a larger attendance drug costs in recent years. He pointed out that although drugs than ever before. As has been happening over the past few account for a large proportion of the total budget, they are re- years, there were even attendees from east of Thunder Bay! sponsible for only about 5% of the cures.

The format of the conference this year was somewhat different Other sessions dealt with Assessment and Consultations, Plan- than it had been in previous years. Each session was opened by ning and Simulation, Immobilization and Delivery, Verification, guest speakers and this allowed the conference to follow a Clinical Trials, Information Management, and Risk Manage- somewhat programmed format. The guest speakers gave presen- ment. The abundance of invited talks in each of these sessions tations on selected topics followed by presentations of relevant provided a great learning opportunity on many topics, such as works in progress. There were also a large number of poster risk management, that normally wouldn’t surface at a WESCAN presentations for viewing and a commercial exhibit area. Repre- meeting. sentatives of some of the commercial vendors hosted workshops highlighting some of their products. Since the abstracts for the As always, there was much spirited discussion taking place dur- works in progress are being published elsewhere in this newslet- ing the sessions. The relatively small, friendly, and informal ter, the following comments deal mostly with the invited talks. atmosphere of the WESCAN conference is particularly suited to promoting this type of interchange of ideas. The discussions The conference opened with a session on “Cancer care – Where spilled over into a number of excellent social events, including a are we now?”. This session gave three speakers the opportunity special St. Patrick’s day event. [note: pictures on p. 74] to present us with a patient perspective, a provider perspective, and a provincial perspective on this subject. The same three in- For the die-hards, a tour of the Tom Baker Cancer Centre was dividuals spoke at the final session dealing with “Cancer Care – offered on Saturday morning. This was a great opportunity for The Future”. Having the same three speakers both open and outsiders to get a look at two new technologies that Calgary has close the conference was an interesting way of wrapping every- to offer. The first was their new Novalis stereotactic unit. This is thing up. The talks were informative and thought provoking. basically a dedicated high precision 6 MV accelerator with an integrated multileaf collimator system. A dedicated planning To my knowledge, there has never before been a presentation by system is used to plan the treatments and special imaging hard- a patient at the WESCAN meeting. Listening to a patient’s per- ware is mounted in the room for position verification. This is spective at such an event is always a good reminder of why we the only Novalis unit in Canada. One of the presented talks at do what we do. The particular patient in question was also a re- the meeting dealt with the challenges of funding this unit. tired medical oncologist so it was interesting to hear her com- ments on what it is like to be on the receiving end of medical The other highlight of the tour was the Nucletron intraoperative treatment. seed implant system for permanent seed implants of the pros- tate. Dose distributions are calculated based on a 3D volume The provider’s perspective was given by Dr. Stephan Larsson acquired from an integrated ultrasound system. Onboard optimi- and the provincial perspective was given by Dr. Tony Fields zation software can calculate needle locations and seed loadings who is the VP of Medical Affairs and Community Oncology for in real time. Needles are inserted using the standard grid tem- the Alberta Cancer Board. plate approach under ultrasound guidance. After the needles are in place, the machine forms the designed seed train and then After hearing Dr. Fields speak, it is evident that the Alberta loads the seeds into the needles automatically. If desired, the Cancer Board not only has a vision, but also has the resources dose distribution can be updated on the fly. During one of the and the will to bring it about. He spoke of setting firm goals for scientific sessions, the group performing prostate implants with minimizing the time between diagnosis and treatment, the need this system presented very impressive dose-volume statistics for to ensure that surgeons are properly trained and follow proper the implants they have carried out so far. For those centers con- protocols, and the existence of a “patient navigator” to guide sidering starting a prostate implant program, this sophisticated patients through the sometimes confusing path of their treat- system and the intraoperative planning approach as opposed to ments. He certainly left the impression that real progress was the preplanned approach should be given a great deal of consid- being made along these lines to make cancer care more effec- eration. tive. When speaking about the future, he stated that taking an aggressive role in applying what we know about the causes of In summary, the 2005 edition of WESCAN was a great success. (Continued on page 73) 54 51(2) avril/April 2005 Canadian Medical Physics Newsletter / Le bulletin canadien physique médical WesCan 2005 Conference Abstracts

Editors note: For the first time ever (to my knowledge), we are be employed as an alternative method to providing better TBI do- publishing conference abstracts in InterACTIONS. This will simetry. provide broader Canadian Medical Physics community expo- Future Work: The clinical implementation of a Monte Carlo method sure for research and clinical work being presented at small, requires dealing with many details. A friendly software interface be- tween the clinician and the Monte Carlo engine has to be built. Exten- local conferences. This can only benefit us as a whole, and I sive documentation and further testing is also required. look forward to further submissions of this nature from local This method is certainly of academic value. But it is still to be evalu- conferences. In this particular entry, the abstracts are from the ated whether the patients will benefit more as a consequence of imple- Western Canadian Radiotherapy Conference (‘WesCan’), a menting it clinically. multidisciplinary conference including Medical Physicists, Ra- diation Therapists, Electronics Technicians, Mould Room, Ma- chine Shop staff, and even the occasional Radiation Oncologist. Correction of Geometric Distortion in MR Images This year the conference was hosted by the Tom Baker Cancer LN Baldwin, K Wachowicz, BG Fallone - Cross Cancer Institute, Ed- Centre, March 17-19 in Calgary, AB. monton, AB Magnetic Resonance Imaging (MRI) is an extremely powerful di- agnostic tool. Because of the excellent soft tissue information provided WesCan 2005 Abstracts: by magnetic resonance (MR) images, and the flexibility to explore various physical properties of tissue that this modality allows, MRI has Genetic Algorithm in Respiratory Motion Prediction for Four– revolutionized the field of oncologic imaging. Despite these strengths, Dimensional Radiotherapy the applicability of MR to radiotherapy treatment planning is limited by G. Badragan1, A. Chan2, I. Kay1, P. Dunscombe1; 1Medical Physics, the geometric inaccuracies in MR images due to inhomogeneities and Tom Baker Cancer Center, Dep. of Physics and Astronomy, U of C, 2 non-linearities that are inherent in the static and gradient magnetic Dep. of Oncology, Tom Baker Cancer Center, U of C, Calgary,AB fields used to form the MR image. Although the soft tissue detail pro- Four-dimensional or gated radiotherapy for lung tumors is currently vided by the MR image may be excellent, the spatial information may the subject of considerable research. The successful application of this not be ideal for treatment planning. While magnetic field inhomoge- technique requires accurate prediction and /or monitoring of organ mo- neities can be reduced, they cannot be entirely eliminated. Therefore, tion. The purpose of this study is to assess the performance of Genetic this research seeks to develop post-processing techniques to correct for Algorithm (GA) in predicting the parameters which characterize respi- the residual geometric inaccuracies in MR images. The magnetic field ratory motion from a limited number of samples. The Genetic Algo- inhomogeneities and non-linearities inherent in the new Philips 3 Tesla rithm is a stochastic global search and optimization method that mimics clinical magnet recently acquired at the Cross Cancer Institute will be the metaphor of natural biological evolution. The Algorithm is an itera- characterized and the geometric distortion in images will be measured tive process in which new populations are created by elitism, crossover via phantom experiments. The in-house developed phantom contains a and mutation at each step. Over successive generations, the population 3D distribution of approximately 10,000 points that can be used to “evolves” toward an optimal solution. For the objective function in the quantify the amount of distortion throughout the magnet’s bore. The GA, a least mean squares approach was used and the prediction is locations of the points are measured using Matlab software, and the based on fitting a periodic curve to some past history of the respiratory MR distortion is calculated with respect to a standard CT image. This motion signal. Discrete data was synthesized at sampling intervals of: information will be used to correct images so that the soft tissue 0.25s, 0.5s, 0.75s, 1s. The mean value and the standard deviation for (tumor) information provided by MR images can be accurately used for each parameter which characterizes respiratory motion were computed radiotherapy treatment planning purposes in the future. using discrete data and the Genetic Algorithm. The Genetic Algorithm outperformed other algorithms based on gradient search minimization. The improved performance is ascribed Development and integration of a post-reconstructive CT de- to the ability of the Genetic Algorithm to avoid local minima and find streaking algorithm in the radiation therapy treatment planning the global minimum. environment P.S. Basran(1,2), I. Kay(3,4); 1) Dept. of Medical Physics, Toronto- Sunnybrook Regional Cancer Centre, Toronto, ON 2) Dept. of Radia- A Monte Carlo Approach for TBI Dosimetry tion Oncology, U. Toronto, Toronto, ON 3) 4) Depts. Oncology and J. Badragan1, G. Badragan1, P. Dunscombe1; 1Dep. Medical Physics, Physics, U. Calgary, Calgary AB Tom Baker Cancer Centre, Calgary, AB Streak artifacts from high-density substances degrade x-ray com- Background: TBI dosimetry has been always associated with diffi- puted tomography (CT) image quality and may introduce errors in culties, which arise from the special conditions of large fields at high identifying tissues of interest and the subsequent radiation therapy dose SSDs. Previous studies have shown that the knowledge acquired for calculation. The objective of this work is to develop a post- more conventional SSDs does not extend properly for the TBI condi- reconstruction CT de-streaking algorithm for radiation treatment plan- tions. Monte Carlo has been successfully employed so far in many ra- ning CTs and integrate this algorithm in the clinical environment. The diation oncology applications. post-reconstructive algorithm consists of 1) two fanbeam re-projection Objective: Explore the potential of Monte Carlo methods to provide of the original CT image and a segmented image containing only the a better dosimetry for TBI. high-density object; 2) re-scaling the segmented high-density fanbeam Method: Monte Carlo methods attempt to accurately model the projections; 3) merging of the two re-projections; and finally 5) back- physical processes, which occur while radiation interacts with matter. projection of the modified fanbeam projections. This simple method Therefore, is always essential to have a proper model of the radiation significantly reduces the masking effects of the high-density artifacts source to start with. We tried two methods both Monte Carlo based. and allows for more accurate delineation of normal and diseased tis- The next step was to run simulations for the TBI conditions and com- sues. The reconstructed images are then introduced into the treatment pare the results obtained to available measurements. planning system as a secondary image data set which can be fused with Results: We obtained a good model for the radiation source and the the original CT data for contouring purposes. Some examples of the de- comparisons against measurements have shown that Monte Carlo can (Continued on page 56)

Canadian Medical Physics Newsletter / Le bulletin canadien physique médicale 51(2) avril/April 2005 55 WesCan 2005 Abstracts… (Continued from page 55) streaking algorithm will be presented. Does Sufficient Evidence Exist To Support Hypofractionation For Prostate Cancer? A Time and Motion Analysis of Treatment Planning and Delivery M. Carlone*, D. Wilkins, P. Raaphorst; Ottawa Hospital Regional Comparing 3D Conformal Radiation Therapy Versus Permanent Cancer Center, Ottawa, ON *Presently at Cross Cancer Institute, Ed- Seed Implantation for Prostate Cancer monton, AB S. Bernard, G. Graham, S. Iftody, D. Radford Evans, L. Traptow; Dept. A publication by Brenner and Hall in 1999 regarding the use of Medical Physics, Tom Baker Cancer Centre, Calgary, AB hypofractionation for prostate cancer has generated much discussion in At the present time there are several options for treating early stage the literature about fraction size dependence for prostate cancer radio- prostate cancer; including surgical prostate resection, external beam therapy. It is becoming more and more accepted that prostate cancer radiation therapy, brachytherapy or a combination of two or more of has a low alpha/beta ratio, which suggests that hypofractionation may these modalities. be used to effectively treat this disease. The purpose of this presenta- Over the past several years, permanent seed implantation using tion is to review the clinical evidence for this conclusion. Two meth- dine 125 has become a very popular and viable option for early stage ods have been used to estimate the alpha/beta ratio for prostate cancer prostate cancer. Due to the convenience and a decrease in side effects, from clinical data: dose escalation analysis and isoeffect analysis. The many patients are opting for this type of therapy. Over the past 24 conclusions of our investigations are that these two methods are consis- months the Tom Baker Cancer Centre has instituted a permanent seed tent with a low alpha/beta ratio for prostate cancer; however, including implantation program. population heterogeneity results in a considerable increase in the confi- dence interval of the alpha/beta estimate. The increase in confidence limits is so large that the estimate becomes statistically insignificant. Pinnacle Version 7.4 Physics Improvements – All’s Well That Ends Our analysis can be used to understand why prohibitively large confi- Well dence intervals result when using a heterogeneous model, and suggest P.Cadman1, T. McNutt, K. Bzdusek2; 1. Medical Physics Dep., Saska- that clinical data from a much larger survival range is needed to reduce toon Cancer Centre, SK, 2. Philips Medical Systems confidence intervals. The presentation will conclude by showing that A new Pinnacle 3D treatment planning system software release has the method of dose escalation analysis of tumour control is fundamen- recently become available (version 7.4, Philips Radiation Oncology tally limited since the presence of linearly correlated parameters is in Systems, Milpitas, CA) which supports modeling of rounded MLC leaf fact an estimate of the dose of 50% tumour control. ends plus a number of other software enhancements intended to im- prove the overall dose calculation accuracy. In this report, we have provided a general discussion of the dose calculation algorithm and Hepatic Radiation and Concurrent 5FuDR Infusion for colorectal new beam modeling parameters. The requirement for a dosimeter with Liver Metastases: Efficacy and Toxicity good spatial resolution and appropriate energy response is established A. Chan*, A. Wong+, E. Yan*; Deps. Radiation Oncology* and Medi- through comparisons of ion chamber, film and diode measurements. cal Oncology+, Tom Baker Cancer Center, Calgary, AB The dose calculation algorithm and modeling parameters chosen were Purpose: A review of the results of a phase I/II study of concurrent validated through various test field calculations and measurements in- radiation and 5FuDR infusion to evaluate the efficacy and toxicity of cluding a bar pattern, a strip pattern and a clinical head and neck IMRT whole hepatic radiation in liver metastases from colorectal cancer. field. Materials and Methods: Between January 1985 and October 1990, 75 patients were treated with whole hepatic radiation and 5FuDR infusion. 2600 cGy was administered with AP-PA parallel portals to cover the A Comparative Study of Mucosal Dose Distribution for Head & entire liver. 2-cm superior and inferior margins were added to account Neck Cancer Patients using IMRT and Conventional Treatment for respiratory motion. 17 patients received additional 600 to 1000 cGy Planning boost with smaller portals for localized disease. Continuous 5FuDR F. Cao, D. Wells; Vancouver Island Centre, BC Cancer Agency, Victo- (0.11-0.16 mg/kg/day) was given concurrently with the hepatic radia- ria, BC tion. There were 44 males and 31 females. After hepatic radiation, 46 Purpose: Head and neck (H&N) cancer patients often suffer from mu- patients (61%) received additional chemotherapy. cosal toxicities when treated with conventional external beam radiation Results: There were 5 CR’s and 18 PR’s by CT evaluation. 46 patients therapy techniques (lateral pair, anterior supraclavicular). A recent had stable disease and 6 patients had disease progression. The response H&N study conducted at BCCA showed that mucosal complications rate (CR+PR) was 30%. The median survival after hepatic RT was 10.5 were significantly reduced using a seven field IMRT technique. Only months. The 1- and 2-year survival was 40% and 11% respectively. For two of 20 patients had transient grade 3 mucosal toxicity and no grade CR+PR group, the median survival was 16.7 months, compared a me- 4 toxicities were observed. The purpose of this study was to quantify dian survival of 9.2 months for those with stable disease or progres- dosimetric differences to mucosa between conventional and IMRT sion, p = 0.00016 (log-rank). 7 patient developed grade 3 thrombocyto- H&N techniques. penia (<50 x109/L). There was transient elevation of serum ALT (up to Methods: The inner edge of the “mucosa” structure was auto-contoured 2x normal) during the first 3 months after RT in 21 patients. Most pa- (HU = -500) and was defined to be 2mm thick. Dose distributions were tients with disease progression developed jaundice or hepatic insuffi- calculated using Cadplan/Helios v6.27. For IMRT plans, no constraints ciency before death. However, 3 patients developed jaundice without were placed on the mucosa during the optimization process. Dose dis- evidence of disease progression. Two patients recovered uneventfully tributions were also calculated using NRC EGS4 Monte Carlo software and one patient died of progressive jaundice. and an additional module to simulate multi-leaf collimator sequences. Conclusion: Whole hepatic radiation of 2600 cGy is fairly well toler- Dose volume histograms and surface dose areas (based on a cylindrical ated. When given concurrently with 5FuDR infusion, it had resulted in model) were estimated for all plans. partial response and survival benefit in selected patients. The limitation Results and Discussion: No significant differences were noted between of whole hepatic radiation has been the liver tolerance. Further research dose distributions derived from Cadplan versus Monte Carlo. Signifi- should focus on partial hepatic radiation with dose escalation, given in cant regional reductions in mucosal dose were achieved with IMRT conjunction with newer effective chemotherapy for colorectal cancers. plans as compared to conventional plans. It may be possible to corre- late these dose reductions with patient mucosal toxicity. IMRT optimi- zation constraints for mucosa may be warranted to further reduce toxic- ity. (Continued on page 67)

56 51(2) avril/April 2005 Canadian Medical Physics Newsletter / Le bulletin canadien physique médical Optimization in Intensity Modulated Radiation Therapy By Stewart Gaede and Eugene Wong, However, selecting beam directions to achieve a London Regional Cancer Program and desired dose distribution can be time consuming and unintuitive. Moreover, beam directions, when added as free variables, University of Western Ontario, excessively enlarge the search space due to their London, Ontario interdependence with beamlet intensities. Bortfeld et al. (12) showed an example of multiple local minima in beam direction 1. INVERSE TREATMENT PLANNING problems. OPTIMIZATION Dose-volume constraints are often used in inverse Intensity Modulated Radiation Therapy (IMRT) has led treatment optimization. These constraints are of the form “no to a practical means of planning and delivering 3-D conformal more than x% of this critical organ can exceed a dose of y.” radiotherapy to complex cases. IMRT can be characterized by However, Deasy (10) showed that the inclusion of dose-volume beams that have individually defined intensity profiles formed constraints could lead to multiple local minima. Simulated using dynamic multileaf collimators (DMLC). In other words, annealing (13-19) and genetic algorithms (20-22) are common each beam can be thought of consisting of many smaller stochastic algorithms in radiotherapy optimization that allow for beamlets of radiation, each with its own intensity that can be an escape from local minima. These methods are often desired optimized to produce the most favourable dose distribution. because the choice of objective function and constraints are not as limited as its deterministic counterpart. However, even with IMRT requires a method of designing optimal non- stochastic algorithms, they can converge to a local minimum uniform beam intensity profiles given a prescribed dose that is still not guaranteed to be the global minimum. distribution. The use of optimization methods for an IMRT plan is called inverse treatment planning. Because of the large In this report, we describe methods to incorporate number of degrees of freedom, conventional trial-and-error beam directions and dose-volume constraints into the inverse methods are often impractical. The goal is to find the best plan treatment planning optimization problem in order to overcome within the physical limits of IMRT. Clinically meaningful some of the disadvantages of current methods. objectives and constraints of the treatment must be defined.

Gradient search and other iterative techniques are 2. AN ALGORITHM FOR SYSTEMATIC common deterministic approaches to solving radiotherapy SELECTION OF BEAM DIRECTIONS FOR problems (1–9). The most well-known example of a physical IMRT objective function that can be solved with a gradient search method is the mean square deviation between the calculated dose Since IMRT usually involves a large number of beams, distribution and the ideal dose prescription in the entire volume frequently 7-11 beams, the impression is that there are enough (Equation 1). degrees of freedom in the intensity-modulation so that the choice of beam directions is of secondary importance. However, p 2 in complex cases where the PTV surrounds a critical organ or is F r ( D  D ) ¦ i i i (1) surrounded by multiple critical organs, the selection of beam i directions becomes important, even in IMRT (23). Not only can better target dose uniformity and better critical organ sparing be D d w w h e r e i ¦ j ij j is the total dose delivered to pixel i, dij ƒ is achieved, but it is also possible to achieve these goals with a the contribution of the dose delivered to pixel iƒ by beamlet j, wj fewer number of beams than standard IMRT plans which are is the intensity of beamlet j, ri ƒ is the relative importance typically composed of an odd number of equally spaced beams p parameter of the structure containing pixel i, and Di is the (24). A fewer number of beams simplifies quality assurance of prescribed dose to pixel i. (e.g. using relative d o s e , beam setups, faster treatment times, and a lower probability of p p ideally, Di =1 for PTV pixels and Di =0 for critical organ patient movement. a n d normal tissue pixels). However, optimization of beam directions is Importance Parameters, ri, are introduced to complicated due to the dependence of one beam direction on its differentiate between different critical organs’ mean square dose corresponding beamlet intensities and the beamlet intensities of deviation and between the target’s and critical organs’. Often all other beam directions. The result is an excessively enlarged referred to as a weighted least squares objective function, the search space, even when the number of beams is small (2-3). attractiveness of this formulation is that it contains a quadratic Compared to fixed beam IMRT, much less research focuses on objective function subject to simple bounds, such as the non- beam direction optimization (12,17,18,22,23,25-27). negativity in the intensities. For a fixed set of gantry angles and Furthermore, the optimal number of beams to employ is only predefined relative importance parameters, such an optimization considered in equally-spaced fixed beam IMRT (18) and not problem is convex (10). That is, any local solution found by a together with the selection of beam directions. gradient or other downhill techniques is also the global solution (11). We report a non-brute force systematic algorithm (Continued on page 58)

Canadian Medical Physics Newsletter / Le bulletin canadien physique médicale 51(2) avril/April 2005 57 Optimization in IMRT... (Continued from page 57) the beamlet intensities will decrease. Therefore, this criteria helps control the number of beams necessary for an adequate which determines a suitable set of beam directions with the treatment plan. fewest number of beams possible. 2.1.2 Stopping Criteria. 2.1 General Description The beam selection process continues until one of three stopping Our approach is similar to that of Soderstrom and criteria is met: Brahme (28) in that we retain beam directions for a plan 1. If the most recent best beam selection is one in which its composed of Nƒ beams as beam direction candidates for a plan composed of N+1 beams. We start by searching for the best beamlet intensities fail the beam significance criteria, “one-beam” plan. This is accomplished by exhaustively then this addition is rejected and the algorithm stops. searching the beam direction space in 10o steps, optimizing the set of beamlet intensities for each beam direction sampled, and 2. If a beam direction is eliminated from the plan, then the simply choosing the beam direction with corresponding optimal beam direction that ultimately replaces the eliminated beamlet intensities that minimizes the objective function, ie. best beam direction must improve the objective function. If it matches the desired dose distribution. This beam is then fixed in doesn’t, then the algorithm stops. direction only, and the search for the second beam is performed. The beamlet intensities for each beam pair are then optimized 3. When searching for the (N+1)-st beam, if the N-th beam and the set that minimizes the objective function is selected as selection (the one most recently selected) fails our beam the best two-beam plan. Adding beam directions in this manner significance criteria for any (N+1)-beam orientation, then guarantees that the objective function describing the treatment the algorithm terminates and accepts the N-beam plan plan quality will always improve. most recently selected by the algorithm. We add this criteria to avoid an infinite loop. For every beam orientation sampled by the algorithm, we optimize the beamlet intensities by minimizing the weighted 2.2 Prostate Phantom least squares objective function, as in Equation 1. A quasi- newton method was used to solve each fixed beam formulation. We considered a “prostate-like” phantom in which the Although the objective function is simplistic, it is well known prostate gland and seminal vesicles were encompassed by the planning target volume (PTV) which wraps around the rectum. and is an obvious fit for our algorithm, since it involves many 40% fixed beam optimizations. For the final set of beam directions, We prescribed 78 Gy to the PTV and ensured that of the 83% 30% one could use a more sophisticated objective function that rectal volume does not exceed of the dose, does not 90% 5% 96% includes dose-volume constraints to generate the beamlet exceed of the dose, and does not exceed of the intensities. dose (29).

2.1.1 Beam Significance Criteria FIGURE 1 shows the progression of the algorithm at the point where either a beam direction is selected or eliminated. At this stage, the selection of beam directions via the Relative importance parameters were chosen to be the same as above approach may not constitute the optimal set of beam those that satisfy the dose-volume constraints for a standard directions. For example, the first beam direction that is selected IMRT plan composed of seven equally spaced beams. primarily for its ability to minimize our objective function may Corresponding objective function values and term by term be a suitable beam direction for a “two-beam” plan, but it may contributions to the objective function by the PTV, rectum, and no longer be suitable for, say, a “seven-beam” plan. By normal tissue are shown in TABLE 1. unsuitable, we mean a beam that does not make a significant contribution to the multi-field dose distribution. If such a beam Notice that an intermediate six-beam plan selected by the o o o o o o exists in a set currently selected by the algorithm, then it is algorithm (270 ,170 ,220 ,130 ,190 ,70 ) has a lower objective eliminated and the iteration restarts dropping the current function value (F=326.6) than the standard seven-beam IMRT eliminated beam direction. We require that one of the following plan (F=328.4). The algorithm continues until the addition of the o o must hold: eighth beam at 90 caused its parallel-opposed beam at 270 to become insignificant. This suggests that lateral parallel opposed 1. At least one beamlet of an incident beam must have a pairs are not useful, at least with the current set of employed o relative intensity of at least 0.15 (plans are normalized to beams. Therefore, the 270 beam is eliminated and a search is 1 at the isocentre). performed to replace this beam. It may not be surprising that a beam at 90 o was the beam ultimately chosen. However, as 2. At least two beamlets of an incident beam must have a TABLE 1 shows, this addition provided no gain to the quality of relative intensity of at least 0.10. the treatment plan. According to the second stopping criterion, the algorithm stops and the seven-beam plan at angles o o o o o o o If beams with more segments were used, then it makes (270 ,170 ,220 ,130 ,190 ,70 ,290 ) is accepted. The sense to relax this beam significance criteria to account for the corresponding dose-volume histograms, shown in FIGURE 2 increase. It is up to the user to define beam significance in this with all plans normalized to D90, compares the optimal plan situation, realizing that an increase in optimization time is generated by the algorithm, the standard IMRT plan, and the expected. We also realize that as the number of beams increase, (Continued on page 62)

58 51(2) avril/April 2005 Canadian Medical Physics Newsletter / Le bulletin canadien physique médical FIGURE 1: Dose Distributions corresponding to plans generated by the beam direction selection al- gorithm for the prostate phantom. The algorithm proceeds left to right, then top to bottom.

TABLE 1: Beam direction selection algorithm for the “prostate-like” case. *- denotes an insignificant beam. Results of the seven equally spaced beam plan are shown in the last row.

Direction Fmin PTV Critical Normal Organ Tissue (0o) 755.3 228.8 92.4 434.0 (0o,270o) 489.8 48.7 104.9 336.2 (0o,270o,170o) 441.1 49.7 70.0 321.4 (0o,270o,170o,220o) 398.6 46.7 52.0 299.9 (0o,270o,170o,220o,130o) 353.5 51.8 32.3 269.4 (0o*,270o,170o,220o,130o,190o) 333.2 46.9 25.9 260.4 (270o,170o,220o,130o,190o) 336.2 48.1 26.8 261.3 (270o,170o,220o,130o,190o,70o) 326.6 49.0 23.3 254.3 (270o,170o,220o,130o,190o,70o,290o) 318.8 50.5 22.7 245.7 (270o*,170o,220o,130o,190o,70o,290o,90o) 317.8 50.2 22.4 245.7 (170o,220o,130o,190o,70o,290o,90o) 319.3 50.9 22.5 245.9 7 Equally Spaced Beams 328.4 50.7 18.7 258.9 (Continued on page 62)

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Therefore, we propose a new class of formulation of the optimization problem to overcome the iterative nature of the former classes. The result is a formulation that directly maps the minimum objective function value to the corresponding critical organ DVHs. As we pointed out earlier, such DVH constraints will create multiple local minima, and we investigated a new stochastic optimization procedure to solve this optimization problem. The basic goal of this formulation is to minimize the dose to specified fractional volumes in the DVH constraints, while respecting specified dose-volume tolerances and maintaining PTV dose uniformity. In other words, the objective function is designed for critical organ sparing and the constraints are user defined or protocol-based PTV requirements such as the minimum and maximum dose.

3.1 Formulation of the Optimization Problem

FIGURE 2: Relative Dose-Volume Histogram normalized to The objective function, FCritical Organs, is a sum of critical D90 for the “Prostate-Like” phantom. Solid lines represent the organ dose-volume based objective functions,ƒ inmƒ , where jƒ six-beam plan generated by the beam direction selection algo- indexes the constraint of critical organ, k. By design, a hard rithm. A minimum dose of 84% to the PTV and objective func- constraint is used to satisfy user defined or protocol-based PTV tion value of 326.6 resulted. Circled lines represent the seven- requirements. The following formulation of the optimization beam plan generated by the algorithm. A minimum dose of 84% problem is devised: to the PTV and objective function value of 318.8 resulted. Dash-dotted lines represent the standard seven equally spaced NscN plan. This has a minimum dose of 80% to the PTV and objective min FCriticalOrgans ¦¦ fkj function value of 328.4. k 11j where

intermediate six beam plan generated by the algorithm. 2 ­ TOL TOL TOL TOL TOL TOL ½ ª D §V j · D j §V j ·º : D §V j · D j §V j · ° « i ¨ C ¸  C ¨ C ¸» i ¨ C ¸ d C ¨ C ¸ ° ° ¦ iC k ¬ © k ¹ k © k ¹¼ © k ¹ k © k ¹ ° f kj ® ¾ This algorithm has the benefit of providing the user 2 ° ª § TOL j · TOL j § TOL j ·º § TOL j · TOL j § TOL j ·° 100 D i ¨V ¸  D ¨V ¸ : D i ¨V ¸ ! D ¨V ¸ ° ¦ iC « C k C k C k » C k C k C k ° with choices. Some planners may choose the intermediate six- ¯ k ¬ © ¹ © ¹¼ © ¹ © ¹¿ beam plan because it is already an improvement to the standard plan with fewer employed beams. subject to

Dmin d Di d Dmax ,i PTV 3. GLOBAL OPTIMIZATION OF DOSE-VOLUME p (V95 )PTV t (V )PTV BASED INVERSE TREATMENT PLANNING 95 N bl D D w , i The simplest class of inverse planning formulation uses i ¦ ip p weighted least squares objective functions, with importance p 1 parameters, designed to match the dose prescribed to both the wp t 0 PTV and critical organs, but does not directly use dose-volume constraints. Such objective functions are convex for fixed beam In this mathematical expression, NS is the number of critical structures, N is the number of dose-volume directions and guarantee a global solution, but don’t always Ck

TOL j § TOL j · constraints of critical structures, k, D ¨ V ¸ is the intuitively result in a desired dose-volume histogram (DVH). C k © C k ¹ TOL specified dose that a fractional volume V j o f critical Ck

structure k can tolerate without complication, § TOL j · is the A second class of formulation of the optimization D i ¨ V ¸ © C k ¹ problem includes dose-volume constraints that minimize a actual dose received by this tolerance volume, D min mean-squared deviation between the prescribed and actual doses and Dmax are, respectively, the specified minimum and maximum dose to the PTV, and is V p the corresponding to the PTV subject to user defined dose-volume constraints to 95 PTV the critical organs and normal tissues (10,30). This formulation prescribed volume at 95% of the dose, Di is the total improves on the simplest formulation, but has an inherent dose to pixel i, Dip is the dose contribution to pixel i by beamlet weakness. To achieve the best PTV uniformity, the optimization p, wp is the intensity of beamlet p, and Nbl is the total number of process will push the critical organ dose as close as possible to beamlets. the specified tolerance. This is not always necessary or desirable. Simply tightening the dose-volume constraints may reduce the critical organ dose, but may come at the cost of PTV (Continued on page 63)

62 51(2) avril/April 2005 Canadian Medical Physics Newsletter / Le bulletin canadien physique médical Optimization in IMRT... (Continued from page 62) al. modified the algorithm to include a “multi-pass” procedure (37). Here, the procedure is repeated for a given number of One feature of this objective function is that any critical iterations, where the initial region size of the random search organ dose-volume constraint can potentially be exceeded in space, r0, is reduced after each pass. The main attraction of this order to better spare other critical organs. Although we wish to approach is that only a small number of random points is avoid using unintuitive importance parameters, we did invoke a sufficient for each iteration. penalty factor (set to 100 in this study) in an attempt to force any exceeding dose to a particular critical organ to be at least close For our problem, we modified the “multi-pass” to tolerance. This factor is not invoked unless the situation arises procedure by reducing the initial region size vector for each pass where one of the dose-volume points has been exceeded. using the equation

(0) (0) 3.2 Modified Luus-Jaakola Algorithm rp+1 =ȕrp (4)

(0) In order to explore the full potential of our proposed where rp ƒ is the initial region size for the pth pass and ȕƒ is an formulation, we developed a new stochastic optimization initial region size contraction factor. This controls the CPU time procedure to inverse treatment planning that includes dose- of the algorithm. The algorithm stops when the initial region size volume constraints. It is based on the Luus-Jaakola (LJ) vector reaches some predefined tolerance, İ, which is related to optimization procedure (31), which is a direct search the minimum change in beamlet intensities. optimization method with a systematic search region reduction This procedure is compared to a fast simulated that has been used to solve a variety of chemical engineering annealing approach which uses a generating function given by problems.32–35. It essentially involves three steps: the Lorentzian probability density function. Details of this procedure are given by Magaras and Mohan (17). Other 1. Given some initial n-dimensional vector w*, a predefined probability distributions, such as the Cauchy or Gaussian number of random points in the -dimensional space are q distributions could be used, but we choose the Lorentzian chosen around this point via the equation distribution because of its computational ease. w=w*+Mr (2) Although stochastic optimization approaches could eventually converge to a global solution if enough time was where M ƒ is an n-dimensional diagonal matrix with granted, our intent was to focus on shorter optimization runs. randomly chosen diagonal elements in the interval [-1,1], Because of the random nature of such algorithms, we investigate and r is defined as the region size vector with elements, the variability of the different solutions by repeating the ulƒ describing the absolute range of zl. In radiotherapy optimization ten times each with a re-initialized seed of the problems, the components of w are the beamlet random number generator. intensities. 3.3 Lung Phantom 2. The feasibility of each set of random intensities is investigated, and if all constraints are satisfied, then the We considered a lung case in which the PTV was objective function is evaluated. If any set of random surrounded by both lungs, heart, and spinal cord with dose- intensities violates any one of the constraints, it is not volume constraints derived by Emami et al. (38). To control hot considered further. To satisfy the non-negativity spots in the normal tissue, we also enforced that no more than constraints, any negative component of the set of 5% of the normal tissue can receive more than 70 Gy. Seven intensities is set to zero. Only beamlets that pass through equally spaced beams were employed. We prescribed a dose of the PTV are used in the optimization. The remaining 71 Gy to the PTV. To maintain suitable coverage of the PTV, we beamlet weights are set to 0. The best feasible w-value is restrict the isodose curve representing 93% of the prescription stored. Steps 1 and 2 define an iteration. dose to the isocentre must encompass the entire PTV (ie. the minimum dose to the PTV) and specified a maximum dose to 3. At the end of each iteration, the initial set of intensities the PTV to be 110% of the prescription dose. Another PTV dose w is replaced by the best feasible w-value obtained in requirement was that V95 • 96%. Step 2 and the region size vector r is reduced by Ȗ via the equation FIGURE 3 shows the dose distributions for the best and j+1 j worst plans based on the minimum objective function value r = Ȗ ro (3) generated by each optimization procedure. The corresponding where Ȗ is a region contraction factor, jƒ is the iteration DVH is shown in FIGURE 4. For this particular case, the lowest objective function value was obtained using the modified LJ number, and ro is the initial region size. procedure. TABLE 2 breaks down the contribution of each term This sequence is repeated for a predefined number of iterations. to the objective function value for this plan emphasizing the Optimization with Non-linear Score functions and Constraints direct correspondence to its DVH shown in FIGURE 4. algorithm (RONSC) proposed by Niemierko (36) can be viewed as a subset of this procedure. The spinal cord and heart received less dose than the fast simulated annealing procedure as shown in FIGURE 4. The To increase the efficiency of this procedure and make it applicable to high-dimensional optimization problems, Luus et (Continued on page 64) Canadian Medical Physics Newsletter / Le bulletin canadien physique médicale 51(2) avril/April 2005 63 Optimization in IMRT... (Continued from page 63) FIGURE 4: Dose-Volume Histogram for lung plans to demon- strate variability of each optimization procedure due to a change in the seed of the random number generator. Solid lines and dotted solid lines represent the best and worst plans, respec- tively, generated by the LJ procedure. Dashed lines and circled lines represent the best and worst plans, respectively, generated by the FSA procedure: (a) The star represents the maximum dose to the spinal cord; (b) The stars represent the dose-volume constraints for both lungs; (c) The stars represent dose-volume constraints for the heart. The triangle represents the dose- volume constraint for the normal tissue.

FIGURE 3: Dose Distributions for lung plans generated to dem- onstrate variability of each optimization procedure due to a change in the seed of the random number generator: (a) Best plan generated by the modified LJ procedure (F=-1322.8); (b) Worst plan generated by the modified LJ procedure (F=226.8); (c) Best plan generated by the FSA procedure (F=-1211.1); d) Worst plan generated by the FSA procedure (F=16,144.0). (Continued on page 65) 64 51(2) avril/April 2005 Canadian Medical Physics Newsletter / Le bulletin canadien physique médical Optimization in IMRT… (Continued from page 64) that involve simple, modulated beams (39). However, much of the effectiveness of IMRT depends on the inverse treatment planning, in which the intensity distribution is calculated to Organ Fractional Obtained Specified f organ optimize prescribed dose distributions. Volume Dose Dose (Gy) (Gy) In principle, it is clear that the higher the number of L. Lung 1/3 35.2 45 -96.3 beams, the higher the dose conformation potential (24). 2/3 26.3 30 -13.6 However, the degree of improvement for adding an additional 3/3 12.5 17.5 -24.8 beam to a plan diminishes as the number of beams increase. R. Lung 1/3 45.04 45 0.16 Research indicates that it is not necessary to use more than 11 intensity-modulated beams to achieve more than feasible results 2/3 30.14 30 2.08 (18). Also, the mentality is that there are enough degrees of 3/3 17.0 17.5 -0.3 freedom in the intensity modulation so that beam directions are Heart 1/3 41.9 60 -327.2 less important. We developed an algorithm (40) which 2/3 40.1 45 -24.4 systematically selected proper beam directions in the fewest 3/3 19.8 40 -408.0 number of beams possible. Fewer employed beams would mean easier quality assurance, faster treatment times, and less Cord 3/3 40.2 50 -96.4 probability of patient movement. N. Tissue 0.05 51.7 70 -334.0

FCritical Organs - - - -1322.8 An ideal treatment planning system that includes dose and/or dose-volume based inverse treatment planning TABLE 2: Contribution of each dose-volume point for each criti- optimization would allow the user to predefine desirable goals, cal structure to the total objective function values for the best such as points on a dose-volume histogram, and allow the user plan generated by the modified LJ procedure. to choose the optimization routine whose objective is to, at the very worst, satisfy all these predefined goals. We have fast simulated annealing procedure had an advantage in sparing investigated a new formulation of the inverse treatment the left lung better than the modified LJ procedure. There planning optimization problem that consists of an objective existed less variability in the minimum objective function function which attempts to minimize the dose to critical organ values generated by the modified LJ procedure. volumes that produce a risk of complications if a certain tolerance dose to those volumes were exceeded (41). This Notice that the worst plans generated by both critical organ based objective function was constrained by the procedures correspond to positive values of the minimum desired dose distribution to the PTV. The advantage of this new objective function value. The DVH shows that the ipsilateral formulation is that we have developed a direct correspondence lung was the main contributing factor. For the LJ procedure, the between the objective function value and the dose-volume largest term contributing to the objective function was the 2/3 histogram. However, this formulation gave rise to multiple local right lung volume term (F=354.2). This translated into a minima. A new stochastic approach based on the Luus-Jaakola ¥(354.2/100)=1.9 Gy violation of the corresponding dose- optimization procedure (31) was introduced and was applied to volume point. For the fast simulated annealing procedure, the the new formulation for a 2D lung phantom. The advantages of largest term contributing to the objective function was again the the modified LJ procedure include the obvious mode of 2/3 right lung volume term (F = 9636.2). This translated to a escaping local minimum traps, its fast convergence to a solution ¥(9636.2/100)=9.8 Gy violation of the corresponding dose when short runs are desired, and a smaller variability in volume pair. Clearly, the latter procedure produced an solutions when multiple runs are employed compared to fast unacceptable result. There may be some debate whether or not simulated annealing. the worst plan generated by the LJ procedure is acceptable. The DVH for the other critical organs were satisfied and the The algorithms presented here will not change when specified PTV coverage was obtained. generalizing the approach to 3-D, which is a future focus. The only consequence will be the increase in time due to the initial Although only one example is shown here, it should be 3-D dose calculation, as well as the increase in beamlet noted that the modified LJ procedure does not always produce a intensities to be optimized. We have provided two approaches better plan than the fast simulated annealing procedure. The in this report to improve upon inverse treatment planning benefit of the fast simulated annealing algorithm is that, given optimization which have the benefits of achieving optimal enough time, the algorithm will converge to an acceptable radiotherapy plans that are both physically and clinically result. However, it is unpredictable how much time is needed. relevant. This explains why the modified LJ procedure always had less variability in solutions over the 10 runs. ACKNOWLEDGEMENTS

4. CONCLUSIONS This work has been funded by the Varian Medical Systems, the London Regional Cancer Program, and the Ontario Graduate Intensity modulated radiation therapy (IMRT) has the Scholarships in Science and Technology. potential to deliver a more conformal dose distribution to complex geometries than conventional non-IMRT techniques (Continued on page 66)

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66 51(2) avril/April 2005 Canadian Medical Physics Newsletter / Le bulletin canadien physique médical WesCan 2005 Abstracts… (Continued from page 56) determine the treatment volumes cannot, however, easily distinguish Does Intensity Modulation Improve Healthy Tissue Sparing in between cancerous tissue and normal tissue. Since positron emission Stereotactic Radiosurgery of Arteriovenous Malformation? tomography (PET) can more readily differentiate between cancerous BG Clark1; M McKenzie1; JL Robar1; E Vollans1; B Toyota2; A Lee1; R and normal tissues there is great interest in using PET images to deline- Ma1; K Goddard1, S Erridge1; 1Radiation Oncology, BC Cancer ate target volumes for radiation treatment planning. The drawback of Agency, 2Neurosurgery, Vancouver General Hospital, Vancouver, BC. using PET is that tumors appear as ill-defined amorphous regions of The aim of this study is to investigate conformal stereotactic ra- higher activity density, which renders manual delineation highly prob- diosurgery (SRS) techniques and quantify potential advantages of in- lematic. As the manual delineation of target volumes in PET images is tensity modulation for stereotactic radiosurgery of arteriovenous mal- difficult, an automatic tool to delineate target volumes is being sought. formation (AVM). Three methods of automatic target volume delineation are being exam- Twenty patients treated with SRS for AVM between 1998 and 2001 ined: thresholding, edge detection and the marker based watershed were replanned with each of four techniques: circular non-coplanar technique. The accuracy and usefulness of each method will be inves- arcs, dynamic arcs, static conformal fields and intensity modulated tigated using a phantom study with well-defined target volumes and fields (IMRS). Patients were selected for size and irregular target activity distributions. shape; with a maximum AVM dimension at least 20mm or volume greater than 10cm3. Target volumes ranged from 2.12cm3 to 13.87cm3 with a median of 6.03cm3. Resulting dose distributions were analysed The Evolving Role of Radiation Therapists in Basic Medical Re- to determine conformality to AVM, target dose homogeneity and search - How Evolved Are We? healthy tissue dose at 3, 6, 12, 18 and 24 Gy. C. Eccles, B. Guibord; Princess Margaret Hospital, Toronto, ON The results show an improvement in conformality index with dif- At the 2002 CARO annual meeting in Toronto, Radiation Thera- ferences statistically significant (p ” 0.01) between circular arcs and pists presented their experiences in a multi-centre research initiative either conformal or IMRS, conformal and dynamic arcs and IMRS and investigating the effects of cytoprotective agent demonstrating the conformal. The paired differences between dose homogeneity index value of Radiation Therapists in clinical research. They argued their are significant for improvement in moving from circular arcs to either specialized knowledge of technical limitations, clinical workflow, do- conformal or IMRS, conformal to IMRS (p ” 0.001) with no difference simetry, radiobiology and basic science make them valuable resources between conformal and dynamic arcs. to the clinical research team. The normal tissue analysis data shows a substantial reduction in Since October 2002, strides have been made preparing Radiation dose at 24 Gy for all other techniques and an increase in dose at 3 Gy Therapists for key roles in research. In 2001, the Ontario School of for the static field techniques when compared to the arc techniques. Radiation Therapy moved from a diploma granting program to one Overall, no advantage was seen for intensity modulation and the dy- granting Bachelor of Science degrees from the Michener Institute of namic arc technique offers the greatest potential for minimization of Applied Health Sciences and the University of Toronto's undergraduate normal tissue dose at all dose levels. department. Additionally, the evolution of an Advanced Integrated Practice Model at Princess Margaret Hospital has included the creation of six Research Radiation Therapist positions. Each Therapist works Extending the application of EUD to account for stochastic proc- part-time clinically and part-time on a research project or team. Key to esses these roles is the translation of research to clinical practice. These ini- G Cranmer-Sargison1 and S Zavgorodni1,2; Dep. Physics and Astron- tiatives include the development of new planning, scanning and treat- omy, U. Victoria1 BC Cancer Agency – Vancouver Island Centre2, ment techniques, the development, improvement and implementation Victoria, BC of new technologies, as well as data collection, management, analysis, As a method for reporting and analyzing dose heterogeneity, the and presentation. Specifically these roles provide an environment in concept of equivalent uniform dose (EUD) asserts that dose distribu- which the view to publication for therapists as co-authors and authors tions are equivalent if they produce the same biological effect. In addi- is the norm. tion to dose heterogeneity, we considered the case, where the total dose The authors of this paper intend to build on their previous work to a volume element has an associated uncertainty. highlighting the evolution of the role of the Research Radiation Thera- To account for the dose uncertainty, we calculate the mean survival pist at their centre, and drawing upon the U.S. and U.K. experiences as fraction (SF) for a stochastic process. Mathematically, the expression support. for this mean survival fraction is identical to that used by Niemierko (1997) in defining EUD. To distinguish between spatial and probabil- istic dose variations, we define equivalent stochastic dose (ESD) as the Probabilistic Risk Analysis of Patient Safety in Radiation Oncology dose that results in a mean survival fraction given a set of random E. Ekaette1; R.C Lee 1,2,3; P.B. Dunscombe1,4; 1: U. Calgary; 2: Cal- events depositing a dose D in a volume. If D follows a probability den- gary Health Technology Implementation Unit; 3: Institute of Health sity function (pdf), SF(ESD) can be calculated using the convolution Economics; 4: Alberta Cancer Board technique. In the case where the pdf follows a Gaussian distribution, an The process of treating cancer with ionizing radiation analytic expression was derived for SF(ESD). The derived expression (radiotherapy) is complex and subject to errors in the treatment prepa- was verified using the Monte Carlo method for treatments of 60 and 70 ration and delivery process. The potential for morbidity and mortality Gy with the fractional dose fixed at 2 Gy. The expression was then to multiple patients compels a systematic approach to assessment and extended to account for multiple stochastic and spatial dose heteroge- management of risk. neities. In high consequence, low probability hazardous systems such as the The results show that the derived expression allows evaluation of nuclear power industry and the chemical manufacturing industry, prob- the reduction in equivalent uniform dose for a combination of stochas- abilistic risk analysis (PRA) has evolved as a safety analysis tool. More tic and spatial dose variations. recently, there have been attempts to adopt a more quantitative and systematic approach to risk analysis in health care delivery systems using PRA as a tool. PRA is a quantitative and proactive approach to Automatic methods of PET target volume delineation risk analysis that examines all factors contributing to an adverse event L. Drever, D. Robinson; U. Alberta, Dep. Physics, Cross Cancer Insti- including infrastructure failure, operating errors and protocol errors and tute, Edmonton, AB their interactions. PRA identifies their probability of occurrence, and Current radiation therapy techniques, such as IMRT and 3D-CRT, consequences. It complements tools already used in patient safety such rely on the precise delivery of high doses of radiation to well defined as the Health Care Failure Mode and Effect Analysis (HFMEA), a volumes. CT, the imaging modality that is most commonly used to (Continued on page 68)

Canadian Medical Physics Newsletter / Le bulletin canadien physique médicale 51(2) avril/April 2005 67 WesCan 2005 Abstracts… (Continued from page 67) procedure. The institutional requirements for a stable & robust infra- semi-quantitative proactive approach, and Root Cause Analysis (RCA), structure (hardware, software, personnel, and processes) to support the a qualitative and reactive approach to patient safety. Common model- demands of radiotherapy will be provided. To 'close the loop' for ra- ing techniques employed in the current PRA project include event tree diotherapy, some form of outcome analysis is required. In-house pro- analysis task analysis and fault tree analysis. This project will also ex- tocols and multi-institutional clinical trials are one way of standardiz- amine the potential of Bayesian Networks as a modeling technique ing the collection of data to perform this analysis. These clinical trials within PRA. require additional infrastructure support, for both the accruing institu- The results of this PRA of patient safety will inform quality control tion and for the clinical trials data warehouse. A brief overview of the groups and improve incident reporting systems. infrastructure used by the Advanced Technology Consortium and its organizations (QARC, RPC, ET, RTOG), along with some recent ad- vances for radiotherapy trials supported by the National Cancer Insti- An improved derivation of the Joiner expressions for determining tute of Canada Clinical Trials Group will be described. The presenta- a simple D/E-independent method to derive a fully isoeffective tion will conclude by providing a few discussion topics. schedules following a change in dose per fraction. H.M. Elmehdi1, S. Pistorius1,2; 1Medical Physics Dep., CancerCare Manitoba, Winnipeg MB, 2Deps. of Physics and Astronomy & Radiol- Radiation therapists’ verification of isocentric placement and error ogy, U. Manitoba, Winnipeg, MB correction during prostate radiotherapy: Do we still need radiation In the paper written by Joiner (IJROBP 2004; 58(3): 871-875), enti- oncologists to review check films? tled A simple D/E-independent method to derive fully isoeffective effec- M. Gackle, J. Wu, C. Newcomb, I. Hudson, S. Merritt.; Tom Baker tive schedules following a change in dose per fraction, the author de- Cancer Centre, Calgary, AB rived two mathematical expressions by which dosimetric errors in de- Background: Conventionally, verification portal images on first day of livering the prescribed dose per fraction in a treatment can be corrected treatment are reviewed by radiation oncologists. A written guideline for. In doing so, the author made an invalid assumption in which he and process was instituted to train radiation therapists (RTTs) to per- assumed D/E is zero for both early and late effects. Even though this form the task independently. assumption is wrong, the author arrived “mistakenly” at the right solu- Objective: To compare isocentric set up errors measured by RTTs to tion. In this presentation, we use first principles to derive these two those measured by a reference radiation oncologist (RO). expressions and the limits at which they cannot be applied, both from Methods: Isocentre set up errors with respect to bony landmarks were radiobiological and mathematical point of views. We also explain the determined on electronic portal images (EPIs) using Varian™/Vision inherent D/E-independence of the expressions. anatomy matching software. Any systematic isocentre error over 3 mm (by averaging 3 days of EPIs) would be corrected by adjusting the table position. Three systematic errors (right-left, ant-post, sup-inf) were Innovative Immobilization for Conformal Radiation Treatment of determined for each patient. Over a one-year period, 100 patients, Extremity Soft Tissue Sarcoma whose EPIs were reviewed by RTTs, were randomly selected to have C. Euler, A. Parent; Radiation Therapy Department, Princess Marga- their EPIs independently evaluated by a reference RO. The goal was to ret Hospital, Toronto, ON achieve ”1.5 mm (within 2 standard deviations) difference between the Conformal radiation planning techniques permit escalated tumour RTTs and reference RO. doses with decreased tumour margins and decreased dose to normal Results: Each of the 297 anatomy matches were evaluated in the three tissues. Efficient immobilization is imperative to accurately deliver the directions: right-left, ant-post, sup-inf. The data was analyzed using radiation as prescribed. Pearson Correlation Coefficient. All three directions demonstrated sta- Present immobilization obstacles in treating sarcomas include an tistical significance and high correlation but only the right-left direction inability to fix the mould to a variety of planning and treatment met the original criteria of ”1.5 mm. However, further investigations couches. Fixation provides setup reproducibility from CT simulator to demonstrated the ‘Law of Averages’ worked to an advantage. The treatment couches as well as MRI and PET. Studies have indicated that measured offset difference between the RTTs and reference RO, aver- increased skin dose may result if immobilization devices are used in aged over three days, validated the objective of ”1.5 mm (within 2 the pre-operative treatment area, potentially leading to wound healing standard deviations) complications. Currently available devices are either limited to the dis- Conclusion: With guidelines and averaging over three days, radiation tal region of the limb, or are too large to avoid the treatment region. therapists are able to determine systematic set up errors comparable to The sarcoma group at Princess Margaret Hospital has developed an the radiation oncologist. The high correlation between the RTT and RO immobilization device that addresses these obstacles. It consists of a measurements support the validity of the process. modified uniframe and a vac lok with a versatile fixation device that can be attached to an assortment of planning and treatment couches. The modified uniframe and vac lok provide comfortable and stable Evolution of Breast Irradiation immobilization resulting in less patient movement during treatment. H Gaffney, D Sayers, C Popescu, W Ansbacher, I Olivotto, E Wai, P We anticipate that routine use of this device will minimize patient Truong, J Lee; Dept of Radiation Therapy, BC Cancer Agency, Van- setup times and adjustments after daily image matching, and potentially couver Island Center (VIC), Victoria, BC reduce the incidence of radiotherapy related wound healing complica- Standard breast irradiation involving the use of opposing tangential tions. This new device is vital for highly conformal and IMRT sar- fields with hard or dynamic wedging has limitations. 1. Frequent hot- coma treatment plans. spots are recognized in axilla and infra mammary folds. 2. Scatter dose Current work is examining the effectiveness and accuracy of this to contralateral breast from hard wedges. device using portal and cone beam CT image matching protocols. Technology has provided us with the capability to improve dose homogeneity by using 3D planning, which enables us to introduce novel techniques. One such technique that has been developed is MLC Information Infrastructure Requirements for Radiation Therapy Compensation, which dispenses with hard and dynamic wedges and in C. Field; Dept. of Medical Physics, Cross Cancer Institute, U. Alberta, principle produces a more homogeneous dose. Edmonton, AB This paper will review how breast planning is evolving from tradi- The radiation therapy process is becoming increasingly complex. tional wedge tangents to compensation using MLC shaping, and to as- The use of 4D and multi-modality imaging for virtual simulation, along sess effectiveness. At present, the VIC is involved in a study compar- with increasingly complex delivery techniques is rapidly escalating the ing conventional wedge planning to MLC compensation planning. amount of information generated before, during, and after a treatment (Continued on page 69)

68 51(2) avril/April 2005 Canadian Medical Physics Newsletter / Le bulletin canadien physique médical WesCan 2005 Abstracts… (Continued from page 68) The results show almost no evidence of the streak artifacts in the MLC compensation is formulated by a manual forward planning dose map. Work will continue with patient images to see if streaks are method, using individual sub fields. With the recent installation of the still negligible in cases of bi-lateral hip prostheses. Eclipse Planning System at the VIC, there are tools available to allow us to automate a new “Field in Field (FIF) planning procedure. It also makes treatment delivery more efficient by performing automated dy- Improving the spectral dose-response of an a-Si EPID namic step and shoot MLC. C. Kirkby, R. Sloboda; Dept. of Medical Physics, Cross Cancer Insti- We will compare the two previously mentioned techniques tute, U. Alberta, Edmonton, AB (Conventional and MLC Compensation) to the newer FIF technique. Amorphous silicon electronic portal imaging devices (a-Si EPIDs) Factors that will be considered are: homogeneity of dose distributions, demonstrate great promise as tools for dose measurement, offering an resource implications for Treatment planning, delivery and staff train- efficient alternative to other two-dimensional dosimeters such as film. ing. This is in anticipation of using the FIF technique for Breast Radia- To date they have been applied for pre-treatment field verification and tion Therapy as a Standard. compensator measurement, and show promise to eventually provide a means to online dose verification during treatment. Recently, it has been reported that the generally linear response of Alternatives to anesthesia for pediatric immobilization in Radio- an a-Si EPID to dose displays some variation when comparing open therapy fields to those attenuated by compensators. We have demonstrated that C. Harris; CancerCare Manitoba, Winnipeg, MB this variation can be greater than 4 % of the open field measurement at Traditionally treating pediatric patients using any of a variety of 6 MV. It has also been established that EPIDs employing high Z scin- Radiotherapy techniques has always had a common concern, immobili- tillation screens such as Gd2O2S:Tb, have an increased sensitivity to zation. The challenge of holding still for the required time can be a low energy (< 1 MeV) photons, which we demonstrate is the cause of problem for many patients and is exacerbated by the young age of this discrepancy. Using Monte Carlo techniques, we modeled both the some, even when shells or other devises are employed. During the past energy specific dose-response of a commercial EPID (Varian aS500) as year a conversation about the quasi-hypnotic effect a cartoon has on a well as the spectral shifts of a generic 6 MV Varian Clinac photon small child prompted a more serious discussion regarding the merits of beam arising from transmission through steel shot compensators up to providing entertainment to distract the patient during setup and treat- 4.5 cm thick. These results were combined to simulate the scenario- ment. At the time a small child was having difficulty holding still for specific detector response. Subsequently, we were able to determine her treatment and was struggling against her shell creating difficulties that by using an external copper plate suspended above the EPID, the in delivering treatment, examining the options, we decided to try a dis- beam could be effectively “pre-hardened” to reduce the observed dis- tractive method to secure her co-operation. crepancy to ~1%. Experimental measurements confirm this finding. Using a commercially available portable DVD player with built in TFT screen; we developed a lead shielded multi-positional stand so that the child can have a clear, unobstructed view of their favorite character Assessment Of Patient Positioning And Patient Motion Using Daily without compromise to comfort or optimal treatment. This initial pa- MVCT Imaging tient immediately became compliant once Spongebob Squarepants was M. MacKenzie, C. Field, D. Weber, T. Campbell, B.G. Fallone; Dep. deployed, and went on to complete her course of therapy without prob- Medical Physics, Cross Cancer Institute, Edmonton, AB lem. Subsequent pediatric patients have had similar results and we have Helical tomotherapy is a highly conformal external beam modality actually cancelled anesthesia where it was thought to be required. that represents a convergence of three dimensional imaging and inten- This presentation will look at the cases this technique has been used sity modulated radiation therapy (IMRT). It is only with the aid of for, describe the methods for building the device and use an algorithm daily MVCT imaging that a truly image guided adaptive radiotherapy to explain the histogram on the finer points of Spongebob and his un- (IGAR) means of delivering IMRT can be realised. Accurate delivery dersea cohorts. of the planned dose distribution is, however, still highly contingent not only on accurate patient positioning, but on sufficient patient immobili- sation as well. Do CT streak artifacts affect dose calculations, or are they just un- An analysis of initial patient positioning and patient shifts required sightly? for patients treated to date is presented. This analysis looks at the re- I. Kay(1,2), P.S. Basran(3,4); 1) Dept. Medical Physics, Tom Baker sults using the different rigid body fusion options available Cancer Centre, Calgary, AB 2) Depts. Oncology and Physics, U. Cal- (translations vs. translations and rotations), the need for manual inter- gary, Calgary AB 3)Dept. of Medical Physics, Toronto-Sunnybrook vention in both translations and rotations, and the reproducibility for Regional Cancer Centre, Toronto, ON 4) Dept. of Radiation Oncol- daily patient position. ogy, U. Toronto, Toronto, ON MVCT data was also acquired for a number of patients both before Streak artifacts from high-density substances certainly interfere and after treatment. Based on these pre and post delivery scans, an with visualization of patient anatomy in CT images, but do they really analysis is made of both the intra-fraction motion on this subset of pa- affect the dose calculations. Some planners, under the impression that tients. it matters, painstakingly contour the streaks and override their density before doing the dose calculation. While some literature exists sug- gesting that the streaks themselves are negligible the demonstration Direct calibration of ion chambers in linac photon beams was based on purely synthetic, numerical simulations. M. McEwen, C. Ross; Ionizing Radiation Standards, Institute for Na- We have acquired CT images of metal rods in a water tank. Dose tional Measurement Standards, NRC, Ottawa, ON distributions were calculated assuming a homogeneous medium Currently, the starting point for dosimetry in the radiotherapy clinic (density 1g/cc), and using heterogeneity corrections, but with the metal is an ion chamber calibrated at the standards laboratory in a 60Co object contoured and its density over-ridden to be 1g/cc. The differ- beam. Conversion factors obtained from a protocol such as TG-51 are ence between dose maps is due to three effects: high densities around then required to derive the dose in a linac beam. The installation of a the metal rod which are artifacts of the CT imaging process that were clinical linac at the Institute of National Measurement Standards in missed in the contouring; differences remote from the rod which were Ottawa in 2002 offered the possibility of directly measured calibration due to the presence of the streak artifacts and differences near the sur- factors for ion chambers in megavoltage photon and electron beams. face of the water due to waves excited by the couch motion. The last The first stage of this work on photon beams has been completed. problem was removed by adding a contour at the surface and overrid- The NRC primary standard water calorimeter was used to calibrate a ing the density. (Continued on page 70)

Canadian Medical Physics Newsletter / Le bulletin canadien physique médicale 51(2) avril/April 2005 69 WesCan 2005 Abstracts… (Continued from page 69) tion flows within any department. Although creating and maintaining set of NE2571 Farmer-type ion chambers in 6, 10 & 25 MV photon an intranet can be a daunting task and to be useful an intranet must be beams from an Elekta Precise linac. The standard uncertainty in the able to respond quickly to the users changing needs. calibration of a chamber is estimated to be 0.4% and the results are in We present an intranet which allows a modular design for rapid good agreement with previous measurements using the NRC Vickers development and customization through the use of extended markup research linac reported by Seuntjens et al in 2000. As a further check, language (XML) templates and configuration files. intercomparisons are currently underway with other national standards In operation for just over 6 months, the system developed at the laboratories and initial results are encouraging. TBCC currently manages many functions in the department including; The experimental set-up of the new clinical linac at INMS means strategic goals and objectives, notice board, vacation and duty calen- that it is relatively simple to calibrate user ionisation chambers directly dars, patient workflow, machine QA and reporting. Providing a basic in megavoltage photon beams using the NRC transfer standards. This infrastructure and incorporating best business practices the system is approach provides a direct test of each chamber in the beams in which being continually expanded to meet information management needs of it will be used and removes the need for calculated conversion factors, the department. resulting in a lower overall uncertainty. It is hoped to offer a calibration service some time in 2005. Prostate Brachytherapy Program at the Tom Baker Cancer Cen- ter. Dosimetry Measurements of a Novalis Stereotactic Unit J. Parsons, Tom Baker Cancer Centre, Calgary, AB G. Menon, D. Spencer, I. Kay; Dep. Medical Physics, Tom Baker Can- Patient eligibility criteria for this procedure are outlined followed cer Centre, Calgary, AB with a summary of the contraindications and advantages of the trans- Novalis® Shaped Beam SurgeryTM, is a state-of-the-art stereotac- perineal template ultrasound guided technique. The acute and chronic tic system for radiosurgery and radiotherapy delivery from BrainLAB side effects of prostate brachytherapy are discussed. Provincial and built on a Varian linac. Novalis treats irregularly shaped tumors non- national radiation protection requirements and guidelines that are dis- invasively with very high accuracy to the prescribed plan by shaping tributed to the patients following the treatment procedure are summa- the 6 MV photon beam to match the contour accurately using built-in rized. The issues associated and encountered when planning treatment micro-multileaf collimators (mMLCs) or circular cones. Hence system- procedures are examined. Survival benefits comparing patients treated atic measurements must be performed by acquiring dosimetric data with surgery and those patients treated with external beam radiotherapy before employing the machine for precision treatment. For ascertaining are presented. the dose characteristics, measurements of percent depth dose, relative scatter factors, and beam profiles were carried out, for both MLCs and cones to be input into the BrainScan treatment planning system for Victoria’s Latest Trends dose calculation. The dose characteristics were measured using an ion P. Picco; BC Cancer Agency, Vancouver Island Centre, Victoria, BC chamber and diodes of superior spatial resolution suitable for stereotac- Modern radiotherapy treatment equipment produces a wide variety tic measurements of small fields ranging from 6 x 6 mm2 to 100 x 100 of data that can be used to monitor its health. Two applications of time mm2 and for cone size openings as small as 4 mm. The results of the trend data used at the BC Cancer Agency’s Vancouver Island Centre measurements confirm the stability and the high precision of the ma- (VIC) are presented. chine for providing dose distributions with small fields suitable for 1. Is the linac monitor chamber sealed to atmosphere? stereotactic treatments. In weekly QA tests, linac radiation output is recorded and plotted against time along with data for normalised inverse of atmospheric pressure. If the ion chamber is sealed then the two sets of data will be Imaging with a Bench-top Megavoltage CT Scanner with Cad- correlated, but if the chamber is open to atmosphere they will not. We mium Tungstate-Photodiode Detectors have had two occasions to change monitor chambers in 4 years. Corre- T. T. Monajemi, D. Tu, B G Fallone, S Rathee; Medical Physics, Cross lation coefficients derived from the plots referred to above show obvi- Cancer Institute, U. Alberta, Edmonton, AB ous differences (before & after) ion chamber change for chamber 1 Megavoltage computed tomography (MVCT) is a potential tool for (0.6389, 0.2279) and chamber 2 (0.9321, 0.0275). We intend to use positioning and dose delivery verification during image guided radio- these correlation coefficients to monitor future health of the ion cham- therapy. The problem with most MVCT systems, however, is their low bers. detective quantum efficiency (DQE) which leads to poor low contrast 2. Does image quality of electronic portal imaging devices degrade resolution and high noise. This makes separating the tumors from their with time? soft tissue background difficult. In an earlier study, we investigated the Several image quality parameters (signal/noise ratio, spatial resolution DQE of eight CdWO4 crystals and photodiodes in our system design & response consistency) were monitored monthly over a four year pe- and found it to be 26% and 19% in Co60 and 6MV beams, respectively. riod on four treatment machines using PIPS QC phantom and software. Once we found these reasonably high DQEs, we expanded the eight Preliminary analysis over 1 year has showed that one EPI system ex- element detector to an eighty element detector, and added a rotary stage hibited significant degradation of signal/noise (p= 0.004). This particu- to create a CT scanner. In the study presented here, the focus is the lar unit operates at 18 MV predominantly, so we speculate that photo- difficulties encountered in getting the images from this system as well neutrons may be the cause. as the imaging characteristics of the system, mainly in a 1.25 MeV We believe that the two examples of time trend data presented have beam. We found the biggest problem to be ring artifacts in the images. some practical significance in our clinic. The methods which were employed to eliminate the ring artifacts are presented along with some sample images in 6 MV and 1.25 MeV beams. Some of the important imaging characteristics of this CT sys- Sensitivity Of Objectives And Constraints Of An IMRT Plan To tem, such as the linearity of the CT numbers, low contrast resolution, Patient Set-Up Uncertainty image resolution, and image signal to noise ratio are quantified. N. Ploquin1,2, W. Song1,2, H. Lau3, P. Dunscombe1,2,3; 1Dep. Medical Physics, Tom Baker Cancer Centre, 2Dep. Physics and Astronomy and 3Oncology, U. Calgary, Calgary, AB Intranets – An Expanding Role in Information Management. Objectives: The goal of this study was to assess the impact of set-up C. Newcomb; Dep. of Medical Physics, Tom Baker Cancer Centre, U. uncertainty on compliance with the objectives and constraints of an Calgary, Calgary, AB intensity modulated radiation therapy (IMRT) protocol for head and Intranets can provide a vital infrastructure for managing informa- (Continued on page 71)

70 51(2) avril/April 2005 Canadian Medical Physics Newsletter / Le bulletin canadien physique médical WesCan 2005 Abstracts… (Continued from page 70) trasound scans acquired from 30 patients receiving intra-operative neck cancer. prostate brachytherapy. Standard pre-planning guidelines for prostate Method: A seven-field head-and-neck IMRT plan was generated on the position and dose distribution were used to generate pre-plans and in- Pinnacle Treatment Planning Systems®. Numerical simulations were tra-operative plans for each patient. Pre-plans were then overlaid on then performed, in the three orthogonal directions, to examine the ef- the intra-operative volume (only the intra-operative plan was delivered fect of set-up uncertainty on the approved static dose distribution on to the patient). Dosimetric parameters were compared for each of the eight structures: CTV54, CTV66, Brainstem, Glottic Larynx, Mandi- pre, overlay, intra-operative plans. D90 and V100 for post-plans were ble, Spinal Cord and Left and Right Parotid Glands. In a population compared with literature values for pre-planning techniques. based approach, both Dose Volume Histograms (DVH) and Equivalent Results: Comparison between live and overlay plans showed that the Uniform Doses (EUD) were used to summarize the information con- live-plan provided superior prostate coverage and was better at limiting tained in the dose distribution achieved by the plan. the dose to the urethra. Using a pre-plan on the intra-operative volume Results: With 5mm margins around the Clinical Target Volumes resulted in D90s that were on average 28% lower than those of the in- (CTV), coverage of the CTV54 and CTV66 remained broadly adequate tra-operative plans. The average volume of urethra receiving greater on the bases of the DVHs and EUDs up to 4mm systematic and 2mm than 150% of the dose was above the acceptable tolerance. Post-plans random set-up uncertainty in all three directions. The five organs at risk for these thirty patients resulted in an average D90 of 177.7Gy with of interest in this plan continued to meet the criteria established up to V100 coverage of 94.4%. These values are well above ABS early 4mm systematic and 2mm random error except for the contralateral guidelines for intra-op brachytherapy of D90 between 120.5 – parotid gland, which the protocol is specifically designed to protect. 136.5Gy, and V100 of 76.2 – 84.9%. Conclusion: We have shown that our IMRT plan is robust up to 4mm Conclusion: Using pre-planning guidelines in an intra-operative setting systematic and 2mm random set-up uncertainties in the three orthogo- results in superior prostate coverage with increased dose to the prostate nal directions. This study provides a quantitative link between the CTV and reduced dose to the urethra at the time of post-planning. to PTV expansion and clinical set-up uncertainty.

A Quantified Assessment of the Use of Non-Linear Image Registra- Inverse Planning Dynamic Multibeam IMRT - a Promising Treat- tion in Image Guided Adaptive Radiotherapy ment Technique in Improving Outcomes in Left Breast Cancer R.C. Rivest,1,2,3 T.A. Riauka,2,3 A.D. Murtha,2,4 and B.G. Fallone1,2,3; Patients - a Case Study 1Dep. Physics, U. Alberta, 2Dep. Oncology, U. Alberta, 3Dep. Medi- C. Popescu, I. Olivotto, L. Salter, W. Beckham; BC Cancer Agency, cal Physics, Cross Cancer Institute, 4Dep. Radiation Oncology, Cross Vancouver Island Centre, Victoria, BC Cancer Institute, Edmonton, AB The importance of post-operative radiotherapy in women with An important step in the image guided adaptive radiotherapy proc- node-positive breast cancer in achieving locoregional control and im- ess is the registration of medical images. Image registration has been proving overall survival was shown in several trials. Published analyses used in clinical radiotherapy for a number of years; however registra- confirm that the risk of death due to cardiovascular disease for left- tion systems have been restricted to linear or rigid registration, mean- breast cancer patients, 10-15 years after RT, is associated with the vol- ing that they cannot take into account soft tissue or organ motion with ume of heart irradiated. respect to rigid bony structures. Among its many applications, non- We have developed a method based on inverse planning dynamic linear or deformable registration will allow for more accurate delinea- multiple intensity modulated beams -“Victoria Conformal IMRT” -for tion of tumours and critical structures by correcting for organ motion breast and IMN (CTV) that improves sparing of heart and ipsilateral and patient miss-alignment from image study to study. Since deform- lung compared with conventional techniques. In this work we present able registration is still in its infancy, a standard protocol for the valida- our IMRT method and compare with DIM (Direct Internal Mammary) tion of these systems does not exist. A comprehensive protocol to for a left-sided breast cancer patient that was recently treated in our assess the accuracy of deformable registration systems over a wide clinic. Both techniques used the monoisocentric setup for treating the range of clinical and research applications has been developed. The supraclavicular nodes with anterior-posterior fields. Metrics for plan protocol has been applied to the Reveal-MVS Fusion Workstation from comparison included homogeneity and conformity index for CTV (HI= Mirada Solutions Ltd. The protocol consists of a preliminary phantom percentage of CTV with dose>95%and <105%; CI=volume of CTV study designed to assess the registration of images with well-defined with dose >95%/body volume >95%), V30% for heart and V20% for objects that have known positions, sizes, and shapes. In addition, a ipsilateral lung (volume receiving > 30 Gy and > 20 Gy ). collection of novel and established metrics are used to determine image IMRT resulted in more uniform PTV coverage than did DIM (HI= registration accuracy for both, real and simulated images. Emphasis 0.87 vs. 0.81 ; CI =0.70 vs. 0.50). V30% for heart was reduces from will be placed on non-linear registration applications that are directly 11.6% to 2.5% with IMRT compared to DIM. V20% for ipsilateral related to radiation therapy. Results will be used to further refine and lung was reduced from 30.3% to 11.6%. Victoria Conformal IMRT improve upon existing non-linear image registration algorithms. technique is superior to conventional treatment methods because of the reduction in high doses to heart and lung when regional lymph nodes are included in the target volume. Interobserver Variability in Electronic Portal Imaging (EPI) Reg- istration in the Treatment of Prostate Cancer .J. Runkel, B. Bendorffe, D. Sayers, S. Zavgorodni, P. Truong, E. Dosimetry guidelines for intra-operative treatment planning Berthelet; Radiation Oncology, BC Cancer Agency, Vancouver Island D. Radford Evans1, S. Angylafi 2, S. Husain2, I. Kay1,3, P. Dunscom- Centre, U. Victoria, Victoria, BC be1,3; 1. Tom Baker Cancer Centre, Dep. Medical Physics, 2. Dep. Ra- Introduction: A protocol of EPI registration for the verification of treat- diation Oncology, 3. U. Calgary - Dep. Oncology, Calgary, AB ment fields has been implemented at our institution. A template is gen- Introduction: In 2003, the Tom Baker Cancer Centre implemented a erated using the reference images which is then registered with the EPI real-time live-planning prostate brachytherapy program using low for verification. This study examines the impact of interobserver vari- dose-rate I-125 seeds to treat low risk prostate cancer. Live planning is ability on the registration process. in its infancy in the brachytherapy community, and pre-planning tech- Materials & Methods: 20 patients were selected for the study. The EPIs niques are more commonly used throughout North America. The goal from the initial 10 fractions were registered independently by 6 observ- of this study is to determine if the dosimetric criteria used with the pre- ers. For each fraction, an anterior-posterior (AP) and right lateral planning technique apply to the intra-operative (live) treatment plan- (LAT) EPIs were generated. These were registered with the reference ning setting. images. Two values of displacement for the AP EPI in the superior- Methods: Pre-plans were generated using data from volume study ul- (Continued on page 72)

Canadian Medical Physics Newsletter / Le bulletin canadien physique médicale 51(2) avril/April 2005 71 WesCan 2005 Abstracts… (Continued from page 71) A multidisciplinary team has designed the operational characteris- inferior (SI) and right left (RL) directions and 2 values for the LAT EPI tics and layout of a system to support in-room localization and correc- in the AP and SI directions were established. A total of 2400 images tion of patient position based upon external landmarks or fiducials. and 4800 variables were analyzed. The relationships between the meas- PC-based software applications, in concert with the NDI Polaris In- urements and the patients, observers, and fraction number were exam- frared localization system, have been constructed for testing and clini- ined using linear regression analysis. The proportion of measurements cal evaluation. Using passive and active infrared detectors, 3D posi- within –3mm to +3mm, was evaluated using the F2 test. Multivariate tional data is relayed continuously to a PC with a precision of +/- analyses were conducted to examine sources of variation and potential 0.35mm. Hardware and software elements designed specifically for interactions.  radiotherapy applications take the form of graphic interfaces that dis- Results: Linear regression analysis showed no statistically significant play: offset measurements; depth and target-to-surface distances, couch observer effect for the 4 measurements analysed. A statistically signifi- shift verification; external contour delineation; and volume rendering cant time trend was observed only for measurement AP LR. The pro- tools to aid in isocenter alignment and patient positioning. Additional portion of measurements within -/+ 3mm were: 73.8% for AP LR, clinical applications also allow real-time patient position monitoring 81.3% for AP SI, 66.8% for LAT AP and 78.2% for LAT SI. There during beam delivery. was significant variation of this proportion between observers in the The results presented here include a pilot study comparing the ac- AP SI (pd0.001) LAT AP (p=0.002) and LAT SI (pd0.001) measure- curacy and reproducibility of conventional skin mark setups to those ments. On multivariate analysis an observer effect was seen for meas- recommended by the infrared navigation system. Comparisons were urement LAT SI only. Time trends however, were not apparent. also made of the target-to-surface distances measured by a linear accel- Conclusion: There is no significant systematic observer effect in the erator optical distance indicator and the navigation system. This ongo- registration of EPI. Furthermore, no systematic time trends were identi- ing study aims to fully examine the feasibility of integrating the infra- fied. This provides, in our view, a measure of Quality Assurance, in red navigation system into routine radiotherapy planning and delivery that the process in place for the registration of EPI is reliable and con- and will continue to quantify its accuracy, precision, and efficiency in sistent. various clinical scenarios.

Assembling the Electronic Patient Record The Clinical Implications of Dynamic Therapies G. Stoesz; CancerCare Manitoba, Winnipeg, MB S. Sidhu1,2, N. Sidhu1,2, C. Lapointe2, G. Gryschuk2; 1Deps Physics and Information management and technology in Oncology is changing Engineering Physics, U. Saskatchewan, 2 Saskatoon Cancer Centre, rapidly. Many cancer centers are facing challenging situations in avail- Saskatoon, SK ability of healthcare professionals, increased waiting list and growing Intrafraction motion has long been suspected of causing inaccura- demands to increase efficiency while maintaining cost and quality of cies in the dose delivered to patients. The Saskatoon Cancer Centre service. Reacting to these challenges cancer centers increasingly rely recently purchased a Varian RPM Gating System, which one hopes on IT solutions for help. Historically, these systems have been de- will improve dose homogeneity when intrafraction organ motion is signed and developed by different communities and are typically im- present during treatment. This study attempts to determine how breath- plemented and installed by different companies creating a fragmented ing affects dose distributions in breast patients and evaluates the poten- IT infrastructure. tial for Gating Therapy in improving patient care. Three different treat- System integration can have a profound effect on the efficiency of ment techniques commonly used in the clinic were investigated: physi- clinical workflow activities carried out within the medical physics de- cal wedge compensators (PWs), enhanced dynamic wedges (EDWs), partment and Oncology as a whole. Any medical application on its and step-and-shoot intensity modulated radiation therapy (ssIMRT). own can claim high to moderate success in improving a single clinical Equipment has been designed to simulate respiratory motion to a process. The creation of information exchange among disparate clini- first order approximation. A breast phantom has also been designed to cal applications and induced workflow management can further stream- represent patient tissue and shape. Film was used as a dosimeter and line activities both vertically in a section and horizontally across func- static dosimetry data was used as a control for comparison. Three ve- tional boundaries, resulting in a previously unanticipated return on in- locities of the breast phantom were studied and Gating Therapy was vestment of existing IT infrastructure. Therefore system integration introduced for each data set. Dose area histograms were calculated for has become an urgent requirement and the object of increasing atten- a breast and lung planning target area (PTA) and Normalized Agree- tion. In the past this would have been troublesome to implement with- ment Test (NAT) Indexes were calculated in reference to the static out the development of an intermediate application. The development case. of DICOM, HL7 and XML standards have helped to overcome this Our study shows that the results are dependent on both the respira- difficulty. This presentation provides an overview how IT underpins tory rate and the wedge angle and that deviation from the static case is an organisation’s effort to improve processes and quality of care while highest if the collimator speed is of the same magnitude as the speed of simultaneously assembling the electronic patient record. the target. Generally, there is a large overdosage to the lung PTA and an underdosage to the breast PTA. However, with the implementation of Gating Therapy, these dose discrepancies are dramatically reduced. Patient Specific Quality Assurance for Helical Tomotherapy S. Thomas, M. MacKenzie, C. Field, B.G. Fallone; Dep. Medical Phys- ics, Cross Cancer Institute, Edmonton, AB The Optical Wand Navigational System: An Aid in Daily Pre- Helical tomotherapy (HT) is a platform for delivering inverse treatment Patient Positioning within A Radiotherapy Department planned Intensity Modulated Radiation Therapy (IMRT), which also F. Sie, G. Bootsma, D. Jaffray, J. Siewerdsen, D. Moseley, G. Wilson, enables a highly integrated approach to image guided adaptive radio- T. Rosewall, E. White, C. Chiarot; Princess Margaret Hospital, To- therapy in the clinic. This integrated approach in the TomoTherapy ronto, ON (Funded in-part by Elekta Oncology Systems) system to delivering highly conformal external beam IMRT is not only Current efforts to escalate tumor doses while reducing normal tis- due to an on board megavoltage CT (MVCT) capability, but as well to sue toxicity heighten the need for precision and accuracy during radia- the integrated image fusion, moveable lasers, and highly accurate tion field placement. This has created a clear demand for novel devices couch. Great care must be taken, however, in order to assure that the that bring improvements in precision without sacrificing efficiency. A highly conformal dose distributions that are planned are, in fact, deliv- model for achieving this objective, through the enhancement of current ered as prescribed by this high precision device. skin mark positioning, has been pursued through the integration of a In this presentation, we shall describe the patient specific quality dedicated infrared optical navigation system into a radiotherapy treat- assurance, which employs several software tools, some developed and ment room for routine patient positioning and 3D verification. (Continued on page 73)

72 51(2) avril/April 2005 Canadian Medical Physics Newsletter / Le bulletin canadien physique médical WesCan 2005 Abstracts… (Continued from page 72) time of treatment. Lack of ambiguity in interpretation of the volumet- provided by the manufacturer (TomoTherapy Inc.), and some devel- ric data will provide a wealth of new information that has not previ- oped in house. The most important feature of the QA process is the ously been available. Reaction to this data requires contemplation of integrated ability of the system to export patient delivery sinograms the impact on the relative roles of the radiation medicine disciplines. onto for calculation in a phantom, and the analysis tools for comparing At the limit, over response to this information could paralyze the work- the measured results from this delivery to the calculations. We will flow, or alternatively, offer a unique opportunity for integrated quality discuss results from the film dosimetry system, ion chamber point assurance. These issues will be explored through experience from the measurements, as well as the use of the gamma function to assess the first clinical cases at Princess Margaret Hospital. resulting measured vs. calculated distribution. An in house computer code has been developed which allow the gamma analysis to be con- strained to region of interest. Results for a sample of patients on in Clinical Trial Progress Report – A Phase I/II Tricentre study of 4D house research protocol are presented, as well as for phantom studies Hypofractionated Radiotherapy (55 Gy/16 fractions) for Localized for some up coming in house research protocols. Prostate Cancer J. Wu1, D. Skarsgard2, R. Pearcey3; 1.Tom Baker Cancer Centre, Cal- gary, AB 2. Saskatoon Cancer Centre, Saskatoon, SK 3. Cross Cancer CT-MR Image Registration for Permanent Prostate Implant Post- Institute, Edmonton, AB Dosimetry Objective: To determine acute/late toxicity and tumor control outcome S. Vidakovic1, R.S. Sloboda2; (1) Dep. Physics, U. Alberta, (2) Cross of 55 Gy/16# - 4 fractions-per-week/4 wks in low and intermediate risk Cancer Institute, Edmonton, AB prostate cancer. An effective treatment for early stage prostate cancer is brachyther- Method: A multi-centre study of prostate patients with T1-2, Gleason apy, where radioactive sources are implanted directly into the treatment score 10%. In our study we investigate using a mutual information registration Results: To date, 6 patients have completed protocol treatment, one of algorithm for fusing CT and MR images. We have obtained CT and whom required IMRT. Overall, isocentre adjustments for target (gold MR images of a prostate phantom (CIRS model 53-I, Norfolk, VA) markers) alignment are required in > 50% of the fractions given. Com- implanted with inactive 125I seeds (model MED3631-A/M, NASI, paring EPIs before and during treatment, intra-fraction target move- Chatsworth, CA). Both CT and MR volumes consist of 15 slices, each ment is discernable for some patients. The average fraction time is ~20 3.0 mm thick with no inter-slice gap. The CT volume was acquired minutes. No grade 3 toxicity is observed within first 3 months of treat- with a Picker PQ-500 CT-scanner performing a conventional scan. The ment. MR volume was obtained using a Philips Gyroscan Intera 1.5T MRI Conclusion: The early experience with a new dose-fractionation sched- system with pelvic coil, employing Turbo Spin Echo (TSE) sequence ule (55 Gy/16#) incorporating real-time target imaging and re- with parameters TE/TR= 105/4401 ms. We investigated the ability of a alignment has been satisfactory. Study accrual will continue. 3D rigid body transformation algorithm, based on maximization of mutual information, to perform automatic registration in a volume of Report on WesCan 2005… (Continued from page 54) interest surrounding the prostate. For this work we utilized Analyze 5.0 The many attendees were treated to a number of talks on sub- (AnalyzeDirect Lenexa, KS), a software package for image analysis jects outside the normal range for such meetings. The open dis- (Mayo Foundation, Rochester, Minn.). cussions were fruitful, many old friends had the chance to renew The results obtained so far are encouraging and suggest that mutual acquaintances, and many new friends were made. The medical information-based registration could enable automatic fusion of clinical physics community in western Canada is well served by these CT and MR images for prostate implant post-dosimetry. meetings that promote a true sense of cooperation and friend- ship. Target Visualization and the Role of the Radiation Therapist E. White, D.A Jaffray; Princess Margaret Hospital, Toronto, ON As is usual, a number of speakers from Victoria and Vancouver The development of on-line image guidance technologies is having took great delight in showing pictures of flowers in bloom taken a significant impact on the practice of radiation therapy. It is common “last week”. Patients visiting these centres must be truly amazed to acquire images for assessment off-line to establish systematic errors by the number of physicists they see outside taking such an in- in the placement of radiation fields. With conformal techniques and terest in the local flora. Be that as it may, the weather in Calgary IMRT becoming more conventional, the need for on-line guidance to wasn’t really great (can I put that any more diplomatically?) but correct for random deviations is inevitable. the warm hospitality more than made up for the cold wind. A Novel sources of guidance data will continue to challenge the tradi- big thanks goes out to Dr. Chris Newcomb and all the other hard tional roles of the Radiation Therapist. The form and quantity of this workers that made the conference such a success. data may have unpredictable influence on the ever-evolving role the therapist. Cone-beam CT technology is being brought into clinical use. The wealth of additional information about the patient’s anatomy at the Next year, WESCAN will be held in Regina. Make plans now to time of treatment raises interesting issues surrounding therapist-based attend this friendly, informative, fun, and very worthwhile meet- interventions. ing. The meeting will be great. The last time WESCAN was in An examination of the information provided through the cone-beam Regina, the weather was great too! CT process will assist in determining appropriate interventions at the (Continued on page 74) Canadian Medical Physics Newsletter / Le bulletin canadien physique médicale 51(2) avril/April 2005 73 Medical Physicist

Creating the future of health.

The Department of Oncology and the Alberta Cancer Board (Tom Baker Cancer Centre) invite applications for a full-time academic position as a Medical Physicist at the Assistant Professor level. Duties include education and training of graduate students and residents, as well as research. The Division of Medical Physics is one of 10 Divisions within the Department of Oncology at the University of Calgary. Physicists within the Division are funded by the Alberta Cancer Board and provide clinical physicist services at the Tom Baker Cancer Centre (TBCC). Approximately 2,500 patients per year receive radiotherapy on one of the nine megavoltage units at the TBCC. Eight of these units are Varian linear accelerators, all of which are equipped with multileaf collimators and three of which have aSi EPIDs.Treatment preparation takes place on one of two CT simulators or a conventional simulator with plans generated by the Pinnacle treatment planning system. The TBCC supports active clinical programs in IMRT, brachytherapy including prostate brachytherapy, and stereotactic radiosurgery.There are currently eight faculty physicist positions at the TBCC within a total Physics Department staff of 45. The Department of Oncology is part of the rapidly growing Faculty of Medicine, which is in the process of building a major new research facility. Calgary is a vibrant, multicultural city (population 1,000,000) near the Rocky Mountains, Banff National Park and Lake Louise. Qualifications include a PhD in Medical Physics or Physics, completion of a clinical physics residency, membership in the Canadian College of Physicists in Medicine, and a record of effective teaching and productive research. A strong commitment to the highest clinical standards, and highly developed, interpersonal, teamwork, organizational and leadership skills, are also required. Please submit a curriculum vitae and a statement of career goals, together with the names of three referees, by May 31, 2005, to: Dr. Peter Dunscombe, Director, Medical Physics Department,Tom Baker Cancer Centre, 1331 – 29 Street N.W., Calgary, Alberta,T2N 4N2 Canada.

In accordance with Canadian immigration requirements, priority will be given to Canadian citizens and permanent residents of Canada. The University of Calgary respects, appreciates and encourages diversity.

www.ucalgary.ca

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      DYULO$SULO&DQDGLDQ0HGLFDO3K\VLFV1HZVOHWWHU/HEXOOHWLQFDQDGLHQSK\VLTXHPpGLFDO CURRENT CORPORATE MEMBERS March 23, 2005

CNMC Company Best Medical International, Inc CMS Inc 865 Easthagan Drive 7643 Fullerton Road 1145 Corporate Lake Dr Nashville TN 37217 Springfield VA 22153 St. Louis MO 63132 Phone: 615.391-3076 Phone: 703.451-2378 104 Phone: 314.812-4388 Fax: 615.885-0285 Fax: 703.451-8421 Fax: 314.812-4491 http://www.cnmcco.com www.bestmedical.com http://www.cms-stl.com/ Contact: Mr. Ferd Pusl Contact: Mr. Krishnan Suthanthiran Contact: Mr. Dan Ciarametaro [email protected] mailto:[email protected] [email protected]

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Modus Medical Devices Inc Nucletron Corporation MDS Nordion 781 Richmond St, Ste 201 8671 Robert Fulton Drive 447 March Road London ON N6A 3H4 Ottawa ON K2K 1X8 Columbia MD 21046 Phone: 519.438-2409 Phone: 410.312-4160 Phone: 1-800.465.3666 2276 Website: www.modusmed.com Fax: 613.591.3705 Fax: 410.312-4126 Website: www.mds.nordion.com www.nucletron.com Contact: Mr. John Miller Contact: Ms. Kelly Simonsen Contact: Ms. Debbie Merrithew [email protected] [email protected] [email protected]

Standard Imaging Inc 7601 Murphy Drive SUN NUCLEAR TomoTherapy Incorporated Middleton WI 53562-2532 475-A Pineda Court 1240 Deming Way Melbourne FL 32940 Madison WI 53717-1954 Phone: 1-800.261-4446 Fax: 608.831-2202 Phone: 321.259-6862 Phone: 608.824-2889 http://www.standardimaging.com Fax: 321.259-7979 Fax: 608.824-2992 http://www.sunnuclear.com/ http://www.tomotherapy.com Contact: Mr. Eric DeWerd [email protected] Contact: Ms. Jodi Pachal Contact: Mr. Jeff Simon [email protected] The Ottawa Hospital Regional Cancer Centre (TOHRCC) is recruiting to fill the vacancy of:

Head, Medical Physics

The Ottawa Hospital is one of the largest academic hospitals in Canada with over 10,000 health care professionals staff. The Ottawa Hospital Regional Cancer Centre (TOHRCC) serves a population of approximately 1.2 million peo- ple, and treats 4000 patients with radiation therapy per year. The Regional Cancer Centre resides on two campuses, and has 7 linear accelerators, one cobalt unit, 1 orthovoltage unit, 1 HDR brachytherapy unit, 2 CT simulators, 1 PET CT scanner, one conventional simulator, and is in the process of installing a Tomotherapy unit for image guided IMRT.

The Physics Department within the radiation program of the TOHRCC has 11 Ph.D. Physicists with expertise in ra- diation therapy and imaging physics. The Physics Department is active in a program of treatment support as well as teaching and research. Ottawa has a residency program in Medical Physics, Radiation Oncology, and takes radiother- apy students for their clinical training. The Physicists hold academic appointments in the Department of Radiology at the University of Ottawa and in the Physics Department at Carleton University. A joint program between the two Universities supports up to 20 graduate students in Medical Physics.

The Head of Medical Physics will lead the department in clinical support and provide direction in new clinical thera- peutic development, will provide a leadership role in the academic mission and activity of the department, will foster strong bonds with both universities, will set standards and provide a leadership role in research, education, and will participate in the management of the Regional Cancer Centre Radiation Program.

Qualifications:

™Member of the Canadian College of Physicists in Medicine or equivalent; ™A proven track record in research; ™Ph.D. in Medical Physics or directly related field; ™Experience and background that will support at the minimum an appointment at the associate profes- sor level in the University of Ottawa Department of Radiology, Division of Radiation Oncology; ™Contribute to research, graduate and post-graduate student and resident training in Medical Physics and Radiation Oncology; ™Excellent interpersonal skills; ™Sound judgement and problem-solving; ™Superior organization skills.

If you are interested in helping shape the future of radiotherapy physics in North America, please send your curricu- lum vitae, quoting competition #OH-17447 by May 27, 2005 to: The Ottawa Hospital, Human Resources, 1053 Car- ling Avenue, Ottawa, ON, K1Y 4E9, or fax: (613) 761-5374, or email: [email protected]

Visit us at www.ottawahospital.on.ca

76 51(2) avril/April 2005 Canadian Medical Physics Newsletter / Le bulletin canadien physique médical CHAIR Department of Physics

The Department of Physics invites applications or nominations for the position of Chair for an initial term of up to five years, beginning on July 1, 2005. The Department is composed currently of ten full-time fac- ulty and three staff supporting programs primarily in Engineering and Applied Science at Ryerson. The De- partment has significant research activity in the field of Medical Physics / Biomedical Engineering and new faculty appointments have been targeted in this area. The faculty have a core group of biomedical physicists who have secured external peer-reviewed research funding to establish advanced research laboratories at Ryerson and have extensive collaborations with the surrounding biomedical community in what the City of Toronto has designated as the Discovery District, home to seven world-renowned hospitals and more than thirty specialized medical and related sciences research centers.

The candidate must possess an earned doctorate in Physics or a related field with a strong commitment to high-quality education and research and must be eligible for appointment at the Associate Professor or Pro- fessor level. The candidate should also have a strong track record in research, administration, and profes- sional activities. The successful applicant will be an effective communicator with faculty, students, and up- per administration and maintain scholarly activity in his/her area of expertise.

The Chair will be expected to provide leadership in developing and maintaining research programs, curricu- lum development, establishing strong university relationships with external organizations, effectively ad- ministering resources and be committed to undergraduate and graduate teaching. The Chair should exhibit academic and administrative leadership towards the achievement and maintenance of high-quality degree programs and research. Under the Chair’s leadership, a collegial and vibrant learning environment is ex- pected. The Chair will assist the Department in the development and implementation of an undergraduate and graduate program in the area of Biomedical Physics during his/her term. The Chair will be expected to contribute to the overall aim of this initiative and enhance science education and research in contemporary areas that will ensure the University’s ability to recruit and retain excellent faculty and students.

Applications and nominations should be sent to: Dr. S.A. Boctor, Dean, Faculty of Engineering and Applied Science, Ryerson University, 350 Victoria Street, Toronto, Ontario. M5B 2K3 or e-mail at: sboctor@ee. ryerson.ca. Applications should include a curriculum vitae, a statement of interest addressing the candi- date’s role as administrator, educator, and researcher, and names of three references. The deadline for ap- plications/nominations to be received at the Dean’s Office is 4:00pm, April 22, 2005.

Ryerson University has an employment equity program and encourages applications from all qualified ap- plicants, including women, Aboriginal peoples, persons with disabilities and visible minorities. Members of designated groups are encouraged to self-identify. In accordance with Canadian Immigration requirements, this advertisement is directed to Canadian citizens and permanent residents of Canada.

Canadian Medical Physics Newsletter / Le bulletin canadien physique médicale 51(2) avril/April 2005 77 www.kgh.on.ca

For aLifestyle You’ll Love, ComeKK to INGSTON! Medical Physicist • Cancer Centre of Southeastern Ontario Kingston General Hospital, Kingston, Ontario

Applications are invited for the position of Medical Physicist at the Cancer Centre of Southeastern Ontario at Kingston General Hospital. KGH, a 445-bed academic health sciences centre affiliated with Queen’s University and a Cancer Care Ontario partner, services a population of 500,000 in Southeastern Ontario. Approximately 3,000 new cancer patients are registered annually at the Cancer Centre.

The Radiation Oncology Programme operates four Varian linear accelerators (a Clinac 2100EX, two 2100C/D’s, and a 600EX), a superficial x-ray unit, an LDR remote afterloader, a Theraplan Plus treatment planning system, an AqSim CT simulator, and is acquiring a Varian Clinac 2100IX this summer. Application is being made to acquire HDR afterloading and a new treatment planning system in the coming fiscal year.

The successful candidate will be expected to participate in all clinical, educational and research activities of the Medical Physics Department. Clinical activities include acceptance testing and commissioning of new equipment, calibrations, dosimetry data maintenance, quality assurance, and treatment planning support. All Medical Physicists are expected to be active leaders in the development of technical improvements in the radiation planning and treatment program. CCSEO Medical Physicists support training programs for Medical Physics residents, Radiation Oncology residents, and Radiation Therapists. There are also opportunities to supervise Medical Physics graduate students in the Department of Physics at Queen’s University.

Candidates for this position must be fully trained Medical Physicists, with a postgraduate degree (Ph.D. preferred) and a minimum of 5 years’ post-training experience in clinical radiation therapy physics. Membership in the Canadian College of Physicists in Medicine or equivalent is preferred. Experience with dynamic wedge, multileaf collimation, portal imaging, CT simulation, and Monte Carlo computer simulation plus expertise in networking and administering computer systems would be assets. Applicants must have good evidence of research and/or development activity with credentials and experience that could lead to an academic appointment at Queen’s University.

Situated in Kingston, Ontario, Kingston General Hospital is mid-way between Toronto and Montreal at the gateway to the St. Lawrence River and the 1000 Islands. History, culture, recreation, entertainment and a rich academic community combine to make Kingston a showcase for quality living. A family-oriented centre, Kingston was chosen as one of Canada’s top five cities for business and lifestyle – all good reasons to consider KINGSTON GENERAL HOSPITAL for your future.

Priority will be given to Canadian citizens and permanent residents of Canada, in accordance with Canadian Immigration requirements. Applications are invited from all qualified candidates. Please submit a curriculum vitae and the names of three professional referees, to: L. John Schreiner, Ph.D., FCCPM, Chief Medical Physicist, CCSEO and KGH, c/o Human Resources Services, Kingston General Hospital, 76 Stuart Street, Kingston, ON K7L 2V7 e-mail: [email protected]

We thank all applicants; however, only those individuals to be interviewed will be contacted.

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